Instruction: Determine the sentiment expressed by the user in her review from the provided choices, and respond by selecting one of the available options.

Input:
The sound is very unnatural compared to my AKG K-55 headphones. Bass is fairly good but the mid-range and highs are severely lacking.

Options:
A: very positive
B: positive
C: neutral
D: negative
E: very negative
Answer: D: negative