钢管扣件式脚手架中，连墙杆与架子连接宜靠近主节点设置，偏离主节点的距离不应大于（）mm。
A、100
B、200
C、300
D、400
参考答案：C
He is_____as a leader but he hasn’t _____in teaching.
A．success; many experiences
B．a success; much experience
C．great success; an experience
D．a great success; a lot of experiences
配制碱洗液的碱母液的浓度是（）%。
A.10
B.20
C.40
D.50
