煤与瓦斯突出基本特征包括抛出的煤堆积角小于煤的()。
A.倾角
B.方位角
C.自然安息角
D.堆积角
参考答案:C
--- Hello, can I speak to Mr. Green, please?
--- I’m afraid not. He ______ a meeting now.
A.will have
B.is having
C.had
D.was having
下列焊条牌号中,______是低合金钢焊条。
A.E4303
B.E5015
C.E5515-B2-V
D.E1-13-16