Shouldn't "which" be replaced with "that" in this sample? Please elborate

Question

Please see page 3, question 1, letter D for the sample question. (Scroll down for link)

The diction in regards to this is why I'm confused. Isn't the sentence before the word "which" directive? Shouldn't "which" be replaced with "that"?

Given that these sample questions are from CollegeBoard.org, which is a very credible organization, makes me wonder.

The complete link with the aforementioned sample question is here: https://secure-media.collegeboard.org/digitalServices/pdf/clep/CompModular_fact_sheet.pdf

Answer 1

There is nothing wrong with the word which in this sentence.

In non-restrictive relative clauses, only which is used (except in poetry or some informal speech, where that is also possible). In restrictive clauses, either which or that can be used.

There is an opinion commonly expressed by prescriptivists that only that can be used in restrictive clauses. This is a myth, entirely at odds with actual usage. For example, President Roosevelt said:

Yesterday, December 7, 1941—a date which will live in infamy—the United States of America was suddenly and deliberately attacked by naval and air forces of the Empire of Japan.

In your question, which appears in a non-restrictive clause, so its use is uncontroversial. However, I thought it was important to correct some of the information given in another answer lest you should see a perfectly acceptable sentence on your exam and think it's a mistake.

For more on the controversy, please see this article by Geoff Pullum, one of the authors of the Cambridge Grammar of the English Language.

Answer 2

Which or That?

as told here
If the sentence doesn’t need the clause that the word in question is connecting, use which. If it does, use that.

consider the following example on the link.

Our office, which has two lunchrooms, is located in Cincinnati.

Our office that has two lunchrooms is located in Cincinnati.

These sentences are not the same. The first sentence tells us that you have just one office, and it’s located in Cincinnati. The clause which has two lunchrooms gives us additional information, but it doesn’t change the meaning of the sentence. Remove the clause and the location of our one office would still be clear: Our office is located in Cincinnati.

The second sentence suggests that we have multiple offices, but the office with two lunchrooms is located in Cincinnati. The phrase that has two lunchrooms is known as a restrictive clause because another part of the sentence (our office) depends on it. You can’t remove that clause without changing the meaning of the sentence.

Now, Regarding your question, It is proven that certain food that are ingested aid the learning processes by releasing natural memory enhancers called CCKs, also known as cholecystokinin, which are composed of tryptophan, choline and phenylalanine.

The word "which" should have been correctly used.