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

Input:
Real bummer on this mat because it is very slippery. The thickness and quality otherwise feels great but my yoga class experience was wildly diminished when I couldn't keep my solidly placed because they were sliding in opposite directions on the mat surface. I would not recommend this unless you're planning on using a towel over it (and even then...)

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