局部瓦斯积聚是指瓦斯浓度超过()其体积超过()的现象。
A.2%
B.0.5立方米
C.1%
D.1立方米
参考答案:A, B
句式转换。
1. We don't play soccer every day. (用now改写为现在进行时)
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2. Our school has thirty-seven classes. (用there be结构改写)
3. Tom goes to the beach with his friends. (用last weekend改写)
4. I'd like a mushroom pizza. (改为一般疑问句)
直达式有利于降低运输成本和提高运输服务质量。