Answer: A. Using mundane words such as fantastic or wonderful
Explanation: I used process of elimination to figure this out.
1: It is important to provide the positive and negative features about this product in a review so the answer couldn't be C or D.
2: The point of a review is to say your opinion. So, B is obviously not correct.
3: Mundane words are usually lacking interest or excitement; dull. This is an important thing to avoid while writing a review. So, this is the answer.