上升管保持的“三通”是指（）
A.炉口通
B.上升管通
C.吸气管通
D.集气管通
参考答案：A, B, D
____________ students have more spare time for their hobbies now.
A．A number of
B．The number of
C．A member of
D．Members of
大型反应器类设备若必须采用钢绳捆绑做为主吊点，始吊时能否将绳套锁紧是关键的质量控制点之一。
