How do you answer what duties you would avoid in a job interview?

It sounds to me like a bit of a trap. I would certainly avoid giving a direct answer if possible. I think it is wise to tell a prospective employer what you will do and not what you will not do.

You might say that you will perform the duties listed in your job description or the duties that are expected of your position, and if those duties change during the term of your employment, you would expect to be able to discuss them with your manager.

You should know what is expected of you before you agree to take the job.