已知某肽段的序列为SAMPLER,分子量为802.96,在质谱中不可能出现的质谱峰是()
A.803.96
B.402.48
C.268.65
D.567.32
参考答案:D
下列物质属于纯净物的是 [ ]
A. 食醋
B.天然气
C.含碘盐
D.蒸馏水
We've offered her the job,but I don't know ________ she'll accept it.(2011·山东)
A.where
B.what
C.whether
D.which