Before I jump to my question, a short note about cloze tests from Wikipedia
A cloze test (also cloze deletion test) is an exercise, test, or assessment consisting of a portion of text with certain words removed (cloze text), where the participant is asked to replace the missing words.
Question: I was looking at my friend's English test paper that was prepared by some Chinese teachers. The text for the cloze section was adopted from an article published in Chicken Soup for the Soul: Raising Great Kids: 101 Stories about Sharing. The article can be accessed via Google Books. On that page, the author modifies "bonus" with "positive". The usage doesn't seem right to me.
The Chinese teachers treated that portion this way:
So, when someone does reciprocate, it is an enormous and positive ______.
A. effect B. bonus C. attitude D. contribution
Of course, the suggested answer was in accordance with the original text, which is B. What do you think?