A:vt
B:
C:2vt
D:不能确定
⑴Where is Jimmy?____
⑵What are the sheep doing?____
⑶What are you doing?____
⑷What is Amy doing?____
⑸Is he playing ping-pong?____
A. Yes, he is.
B. He is in the classroom.
C. She is singing and dancing.
D. I'm walking.
E. They're running on the grass.
清朝初期规定了西藏历世达赖和班禅都必须经过中央政权册封的制度。此项制度的主要作用在于( )