下列物质的沸点高低次序正确的是( )
A: t(He)>t(Ne)>t(Ar)>t(Kr)
B: t(He)
C: t(HF)
D: t(HF)>t(HCl)>t(HBr)>t(HI)
A: t(He)>t(Ne)>t(Ar)>t(Kr)
B: t(He)
C: t(HF)
D: t(HF)>t(HCl)>t(HBr)>t(HI)
举一反三
- He must be ill, ______?: doesn’t he|isn’t he|mustn’t he|needn’t he
- 25.It is the third time that John has been late, ______? A. hasn’t he B. isn’t he C. isn’t it D. hasn’t it A: hasn’t he B: isn’t he C: isn’t it D: hasn’t it
- He must be in the library now, ____? A: doesn't he B: mustn't he C: needn't he D: isn't he
- He’s read this book before, ___________ ? A: hasn't he B: isn't he C: wasn't he D: doesn't he
- He must have finished his homework, ____________? A: musn't he B: haven't he C: didn't he D: hasn't he