橄榄石是（）
A.硅酸盐宝石
B.碳酸盐宝石
C.磷酸盐宝石
D.硝酸盐宝石
参考答案：A
—How long have you learned English?
— _____ about five years.[ ]
A. From
B. Since
C. By
D. For
工作班成员对哪些安全事项负责？
