某有机物燃烧后产物只有CO2和H2O,可推出的结论是,这种有机物中[ ]
A.一定只有C、H
B.可能含有C、H、O
C.一定含有C、H、无O
D.一定含有C、H、可能有O
答案:D
根据首字母完成单词。
1. I'm taking a v______ in Hong Kong next year.
2. I didn't have a camera, so I r______one when I went sightseeing in Hawaii last summer.
3 . I waited u______ 11 last night, but he didn't get back.
4. I s______ half an hour watching TV last night.
5. When did your sister get b______ from Thailand?
随机误差不能修正,也不能完全消除,但可以用增加测量次数的方法加以限制和减少。