You should not praise an act of apparent generosity unless you believe

D is the right answer.

The following valid logic diagrams can be drawn from the statements above.
1. An act of generosity that is not out of selflessness ------> that act of generosity should not be praised.
2. Act of generosity should be praised -------> act of generosity that is out of selflessness
3. Act of apparent selfishness that is not performed out of self-centeredness -----> That act of selfishness should not be condemned
4. Act of apparent selfishness should be condemned ------> that act of selfishness is performed out of self-centeredness

With these four valid logical diagrams in mind, let's evaluate the answer choices to ascertain which answer choice follows any of the four valid inferences above.

From the statement in A, Monica had selflessly offered to help in the project hence, from inference 1 above, Monica should not be condemned. Meanwhile the statement says that Caroline rightly blamed Monica. This is thus incorrect.

So Michael told Sarah about his charitable act that he did in the past and Sarah guessed that he only told her that fact to impress her. Sarah guessed, she could be wrong or she could be right. If she is wrong, then her act opposed to the inference 2 above. Besides, the information provided in B above is not direct as we have no way of ascertaining whether Michael's donation was truly an act of generosity performed out of selflessness. Eliminate B.

C is also incorrect because we are unable to determine clearly whether William's failure to make an effort to keep in contact with any of his friends after he moved out of town was out of self-centeredness. Based on this, we cannot tell per the inference 4 whether Enrique is justified to excuse William.

Correct. This is rightly in line with inference 3. Margaret had a selfish motive for offering to share her house with a visiting French family since she only made the offer in anticipation of a reciprocated invitation to use the family's apartment in Paris.

This is incorrect as it violates inference 2 above. Louise felt sorry for the abandoned dog, hence her decision to adopt it is charitable. Per inference 2, her action should be praised and not criticized.