Instruction: Given the user's review, identify the user's sentiment from the listed options. Answer using one of the options.

Input:
Impossible to inflate. Horrible, frustrating experience. I read every single review and answer about how to find a way to inflate this ("pinch the opening while being inflated" etc.), and NOTHING worked. I wound up with a cramped hand and a bad mood. Even called the manufacturer's customer service for assistance--they were unable to help. I only felt better when I was able to return this to Amazon for a full refund.

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