I can’t pretend ________ happy when I am not.

A．to be

B．to have been

C．being

D．having been

呃逆的基本病机为

A．肝气犯胃，胃失和降
B．气、痰、瘀交结，阻隔于食道、胃脘
C．胃气阻滞，胃失和降，不通则痛
D．脏腑经脉失养，不荣而痛
E．脏腑气机阻滞，气血不畅，经脉痹阻，不通则痛