Which survey question is unbiased?

Question

A. “Do you think we should allow them to cut down the trees and pave over the grass for the new playground?”
B. “Which do you prefer with a meal—water, or a syrupy sweet soft drink?”
C. “Should there be a school dress code?”
D. “Do you prefer bringing a healthy lunch to school or eating cafeteria food?”

Answer 1

C. “Should there be a school dress code?”