First off the answer for this catchy question is the second sentence which by the way it's intentionally hidden, has an intended punctuation error or a non-intended briefly slip because of the comma that should never be written down there, in other words:
# 1 sentence: The author's claim is that (of) a diet rich in vegetables/(Wrong option since it never ends up saying the sentence's objective nor the rest; so it's incomplete)
# 2 sentence: Whole grains(,) and beans can help prevent cancer.(Correct option)
