The best way to tackle this question is to go through each answer and pointing out the errors.
"The book, that I borrowed from Elizabeth last week was excellent." The point of this sentence is to say that the book is excellent. The bit in the middle is just anecdotal and it should be removable in between two commas. Therefore, it should be "The book, that I borrowed from Elizabeth last week, was excellent."
"About four thousand years ago, Stonehenge, was a center of worship." In this example, the opening is setting up the rest of the sentence. However, the extra comma is irrelevant. It should be "About four thousand years ago, Stonehenge was a center of worship."
"Athletic excellence requires a number of traits: perseverance, skill, aggression, and discipline." This one is a much simpler- yet subtler- mistake; there is no comma in a list just before the "and". It should be "Athletic excellence requires a number of traits: perseverance, skill, aggression and discipline."
That leaves C) as the correct answer.
