Kate: Do you mind opening the door for me？ Rita: ______.A．Yes, I"ll do itB．It"s nothingC．T

Kate: Do you mind opening the door for me？ Rita: ______.

A．Yes, I"ll do it

B．It"s nothing

C．That"s all right

D．Not at all

请帮忙给出正确答案和分析，谢谢！