Ms Black is considered a________lady by her neighbors, for she often helps the poor old man next door.  [      ]

A. generous  

B. hopeful

C. mean  

D. selfish

酸碱平衡的调节主要是（）。

A.以呼吸系统为主

B.肾脏功能调节

C.血液缓冲系统为主

D.靠以上三者共同作用

E.靠抗利尿素与醛固酮的作用