His MP3 is the same as _____, but it is more expensive. [ ]
A. him
B. mine
C. my
D. her
答案:B
氧中毒的临床表现有()
A.头痛
B.恶心
C.烦躁不安
D.面色苍白
E.进行性呼吸困难
某弱酸性药在pH为4.5时约90%解离,其pKa为()
A.6
B.5
C.4
D.3
E.2