推动血液运行的基本动力是
A.心的功能
B.脾的功能
C.肝的功能
D.肺的功能
E.肾的功能
参考答案:A
Mary had to go to a meeting,so she left her children________at home.[ ]
A.playing
B.played
C.to play
D.having played
The police still haven' t found her, but they' re doing all they ______ .
A.may
B.can
C.must
D.will