呕吐、反胃、呃逆三者在病机上的共同点是（）
A.升降失司
B.肺胃气逆
C.肝胃气逆
D.饮邪上逆
E.胃气上逆
参考答案：E
The little boy was so careless with his spelling that she often_____ letters from words.
A．left out
B．left behind
C．left off
D．let alone
CTCS按运用划分为几级？
