体内样品测定的常用方法()
A.uv
B.IR
C.GC
D.HPLC-MS
E.GC-MS
参考答案：C, D, E
绝对值不大于3的整数的和是______．
I ______ be afraid of the dark. [ ]
A. use to
B. used to
C. are used to
D. are used for
