质谱的离子化方式有()。
A、EI
B、CI
C、APCI
D、ESI
参考答案:A, B, C, D
I have been trying my best to study English I want to have a chance to be a volunteer for the London Olympic Games.[ ]
A.but
B.so
C.because
D.until
质量改进是致力于()。