基础砌筑时砂浆饱满度不得低于()。
A、75%
B、80%
C、90%
D、100%
参考答案:B
He ______ at the meeting, but his heart attack prevented him.
A.will speak
B.is going to speak
C.had to speak
D.was going to speak
怎样启用汽提塔?应注意些什么?