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:
I had to return this product because it did not work for me. However, I'm not criticizing its performance for I was not sure if the problem arose out of compatibility issues with my PC.

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