煤是由什么转变成的,成煤过程包括哪些阶段?
参考答案:
煤是由古代植物遗体经过漫长的时间转变而成的。
成煤过程包括三个阶段分别是:泥炭化阶段、煤化阶段、变质阶段。
单词拼写。
1. It's cheaper if you book the tickets in a_____.
2. I wasn't sure if I could h_____ such a powerful car.
3. She g_____ us through the busy streets to the cathedral.
4. The writer personally c_____$5,000 to the earthquake fund.
5. Police suspect there may be a l_____ between the two murders.
6. He _____(折叠) the map up and put it in his pocket.
7. Just for an_____ (瞬间) I thought he was going to refuse.
8. I'm afraid getting things changed will be a slow_____ (过程).
9. Daytime temperatures vary between minus 5°and _____(零上) 12°.
10. The competition attracted over 500 contestants ______(代表) 8 different countries.
0.5 mol的氢气在标准状况下所占的体积约是 [ ]
A.22.4L
B.11.2L
C.5.6L
D.2.24L