钻孔接近老空，预计可能有瓦斯或其他有害气体涌出时，必须有瓦斯检查工或矿山救护队员在现场值班，检查空气成分。
参考答案：对
She often _____ big plans that never happen. [ ]
A. gets
B. makes
C. does
D. calls
煅烧500kgCaCO3，可以制取CaO（）kg。
A.560
B.280
C.140
D.1120
