1 . The practice of tai chi aims to maintain ______ ______ of yin and yang in the body through opposite movements. Eventually, tai chi brings about a state of physical balance and mental peace. （根据句意填空）

2 . In order to make it clear, I must go   up to________ second floor and ask him________ second time.

A．the; a

B．a; the

C．the; the