The correct answer is D) core benefit.
Christopher works overtime in a project of his office. On his day off, he goes to watch a comedy movie to ease the stress. He finds the movie entertaining and it helps him relax. In the context of product layers, entertainment, in this scenario represents the core benefit of the movie.
The core benefit is the right answer because is the central aspect of the benefit for Christopher in watching an entertained movie. Thanks to this action, Christopher can ha a good time, laughing and in relaxation to forget all the stress caused by the overtime hours spent in the office's project.
The other options of the question were a) implied benefit, b) explicit benefit, and c) combined benefit.