采煤工作面上隅角采用风筒导引瓦斯时,风筒内的瓦斯浓度应()。
A.在1.5%以下
B.不超过1.5%
C.在3.0%以下
D.不超过3.0%
参考答案:D
To enjoy the scenery, Sara would spend long hours on the train _______ travel by air.[ ]
A. other than
B. rather than
C. more than
D. instead of
试述政治社团在现代政治生活中的作用。