Are you able to provide the rules about that one?
If you key it up in Microsoft Word, it will tell you. 
It’s all about whether the clause the relative pronouns is standing in for is “restrictive” (the sentence falls apart if you leave it out) or “non-restrictive” (you could discard the relative clause without affecting the meaning of the main clause).
http://grammar.uoregon.edu/pronouns/relative.html
Determining the correct relative pronoun:
When information is critical to the understanding of the main clause, use THAT as the appropriate relative pronoun and do not set the information off by commas. The clause containing the pronoun and not set off by commas is referred to as a restrictive clause.
(Restrictive)-- That
Russian generals have delivered a message that is difficult to ignore.THAT relates back to the noun MESSAGE and is necessary for the reader to know what MESSAGE the sentence is about.
Clinton will continue to hammer out a historic Mideast pact that bears his stamp.
THAT relates back to the noun PACT and is necessary for the reader to know what PACTthe sentence is about.
There is another factor that obviously boosts the reputation of both of these men.
THAT relates back to the noun FACTOR and is necessary for the reader to know what FACTOR the sentence is about.When information is NOT critical to the understanding of the main clause, use WHICH as the appropriate relative pronoun and set the information off by commas. The clause set off by commas is referred to as a nonrestrictive dependent clause.
(Nonrestrictive)-- WhichNonrestrictive relative pronouns describe, add incidental detail or begin new/separate ideas. There is usually a comma separating the non-restrictive clause from the main/independent clause
The toughest intramural fight of all for Clinton was the North American Free Trade Agreement, which he undertook a full year before the 1994 election.
WHICH relates back to the noun AGREEMENT and the information following it is not necessary for the reader to know what AGREEMENT the sentence is about.
Clinton refused to head toward the center on affirmative action and abortion, which are the two most sacred issues to the traditional liberal wing of the party.
WHICH relates back to the noun AFFIRMATIVE ACTION AND ABORTION and the information following it is not necessary for the reader to know what AFFIRMATIVE ACTION AND ABORTION the sentence is about.
That is a relative pronoun used in restrictive clauses. Which is a relative pronoun used in nonrestrictive clauses. Who is a restrictive pronoun used in sanity clauses, but everyone knows there’s no such thing as a Sanity Clause.
From American Heritage Book of English Usage
that / which (restrictive and nonrestrictive clauses). > The standard rule requires that you use that only to introduce a restrictive (or defining) relative clause, which identifies the person or thing being talked about; in this use it should never be preceded by a comma. Thus, in the sentence The house that Jack built has been torn down, the clause that Jack built is a restrictive clause telling which specific house was torn down. Similarly, in I am looking for a book that is easy to read, the restrictive clause that is easy to read tells what kind of book is desired. 1
By contrast, you use which only with nonrestrictive (or nondefining) clauses, which give additional information about something that has already been identified in the context; in this use, which is always preceded by a comma. Thus you should say The students in Chemistry 101 have been complaining about the textbook, which (not that) is hard to follow. The clause which is hard to follow is nonrestrictive in that it does not indicate which text is being complained about; even if it were omitted, we would know that the phrase the textbook refers to the text in Chemistry 101. It should be easy to follow the rule in nonrestrictive clauses like this, since which here sounds more natural than that. 2
Some people extend the rule and insist that, just as that should be used only in restrictive clauses, which should be used only in nonrestrictive clauses. By this thinking, you should avoid using which in sentences such as I need a book which will tell me all about city gardening, where the restrictive clause which will tell me all about city gardening describes what sort of book is needed. But this use of which with restrictive clauses is very common, even in edited prose. If you fail to follow the rule in this point, you have plenty of company. Moreover, there are some situations in which which is preferable to that. Which can be especially useful where two or more relative clauses are joined by and or or: It is a philosophy in which ordinary people may find solace and which many have found reason to praise. You may also want to use which to introduce a restrictive clause when the preceding phrase contains a that: We want to assign only that book which will be most helpful.
omitting that. > You can omit that in a relative clause when the subject of the clause is different from the word or phrase the clause refers to. Thus, you can say either the book that I was reading or the book I was reading. You can also omit that when it introduces a subordinate clause: I think we should try again. You should not omit that, however, when the subordinate clause begins with an adverbial phrase or anything other than the subject: She said that under no circumstances would she allow us to skip the meeting. The book argues that eventually the housing supply will increase. This last sentence would be ambiguous if that were omitted, since the adverb eventually could then be construed as modifying either argues or will increase.
that instead of who. > The man that wanted to talk to you just called back. Some people say that you can only use who and not that to introduce a restrictive relative clause that identifies a person. But that has been used in this way for centuries. It is a quintessential English usage, going back to the Old English period, and has been used by our best writers. So it is entirely acceptable to write either the man that wanted to talk to you or the man who wanted to talk to you.
As you can see, there’s a little bit of a loophole where which is concerned should you care to exercise it.
sigh Betrayed by mine own keyboard … of mine.
Looks like you’re coming along nicely.
An old term from the days of sail.
By the wind means “as near as possible to the direction from which the wind is blowing.” Large means that the wind is crossing the line of a ship’s course in a favorable direction, such as from behind.
Thus by and large means “on the whole,” “almost entirely,” or “generally.”
I have a friend who says “Velcrove”. I think it’s a hardware thing.
Nucular.
No, I prefer this: I’m the ticket starving to death.
Mine is “that” instead of “who.”
e.g. a company near us which advertises: Plumbers that care!
Then there was my 10th grade geometry teacher who’d say
“Now let’s do number A.”
That’s the ticket! 
I hate the phrase “truth be told” or “truth to tell”. When I see those in a book I want to immediately throw the book in a fire. Ewuii, shudder 
About WHICH one?
Oh, BTW, are you looking for the largest number? or the total number? or the greatest number?
I’m looking for the mostest.
American Heritage puts the blessing on using that instead of who, stating that
- That has been used that way for centuries.
B. It is quintessential English usage.
III. It dates back to Old English.
And finally, it is used by some of our best writers.
Hmph. Shouldn’t that be, “a company who advertise”? 
Oh. I still don’t like it. Sounds dorky.
Nah. “A company wot advertises.” Standard English, mate. Innit.
sigh
And here I was trying to be so veddy veddy British. I need to watch Eastenders some.