A: May I bring a radio on a camping trip?

Question

B1: No, you must bring it.
B2: No, you must bring one.

(Which answer is right? Do we have to use 'one' or 'it' as the answer to the question?)

Answer 1

Either answer is self-contradictory.

May I bring a radio on the camping trip?
Yes, you may bring one.

Answer 2

(Oh, I made a mistake. It is a little cold in my country. My hands feel a little cold, so it's a little difficult to type on the keyboard.)

A: May I bring a radio on a camping trip?
B1: No, you must not bring it.
B2: No, you must not bring one.

(Do you mean 'one' is right?)

Answer 3

Between these two choices, B2 is better. Either one is grammatical, but B2 is better.