肺泡内的氧气进入血液中的红细胞,要经过( )层细胞膜.
A:五
B:二
C:三
D:四
已知函数f(x)=excosx﹣x.
⑴Doing more exercise is good for health. ____
⑵I feel cold. I need to wear warm clothes. ____
⑶You should see a doctor when you are ill. ____
⑷If you are angry, you'd better take a deep breath and count to ten. ____
A.
B.
C.
D.