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:
These are most effective when used with mittens rather then gloves.  They last a long time but give them 15 monutes to heat up in the air.

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