硫化氢的来源及特点有哪些？（） A.浓度达到4.5-43.7%遇火会爆

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硫化氢的来源及特点有哪些？（）

A.浓度达到4.5-43.7%遇火会爆炸

B.无色、微甜、毒性极强

C.来源于炸药的不完全爆炸

D.从旧巷道煤岩中放出

答案

参考答案：B, C

完形填空

66	Ann works hard at English. She never wastes time.
67	Bill is always afraid of failing exams. He needs more confidence.
68	David has good study habits. He thinks the beginning is very important.
69	Linda is 70 years old, but she still likes learning something.
70	Tom wants to be a professional basketball player, but he can’t play it very well.

A. Practice makes perfect.	B. Every minute counts.
C. Failure is the mother of success.	D. A good beginning is half done.
E. It is never too old to learn.

名词解释

蒙古高压