“That” vs. “Which”
People have expressed a desire to know more about when to use that instead of which. The easiest way to think about it is that is necessary and which is just additional info. If I have only one computer, I can say, “My computer, which is on my lap, is a Fujitsu.” If I have more than one computer, I should say, “The computer that is on my lap is a Fujitsu.” (Note the use of commas in both.) The latter will distinguish this computer from my Gateway computer, which is on the coffee table, and the custom build, which is in my office.
I missed this one on FaceBook, and I’ve always had trouble that/which-ing. Glad I came and checked your site!