()的确定,是辨识危险源的基本条件。
参考答案:作业活动
22. — When did you last see your first teacher?
— On_____Friday last June, at_____celebration of her 40th year of teaching.
A.a; the
B.a; a
C.不填; the
D.不填; a
一般输送机送原煤,向上运输倾角最大可达多少?