Set of techniques; singular or plural?

Question

I have an English course book that contains this question:Fill in the blank"The book is a set of techniques that systematically ______ the learner for interaction with target language speakers". (A) prepare (B) preparing (C) prepares (D) prepared." The answer given in the book is A, but isn't C correct?I used Google and found this example "DNA technology is a powerful set of techniques that ALLOWS scientists to examine, change, and create new genetic material"

Answer 1

Yes- you have to find the subject of the verb, which in this case set, which is singular. Good work!