多巴胺增加肾血流量的主要机制是( )
A.兴奋β1受体
B.奋β2受体
C.兴奋多巴胺受体
D.阻断α受体
E.直接松弛肾血管平滑肌
参考答案:C
—Can you give me a hand, Robin?
—But, Helen, you ____ my help every five minutes. I ___ TV now. [ ]
A. need, am watching
B. need, watch
C. are needing, watch
D. are needing, am watching
若二叉树的先序遍历序列为ABDECF,中序遍历序列DBEAFC,则其后序遍历序列为()
A.DEBAFC
B.DEFBCA
C.DEBCFA
D.DEBFCA