Instruction: Carefully assess the user's review for any strong expressions of sentiment, either positive or negative. Based on your analysis, select the most fitting sentiment option from the provided list as output.

Input:
Not confident about putting full weight on it in exercise routines, would buy a thicker-walled unit that doesn't fold into a box so neatly.

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