As one of the tools and techniques of activity sequencing, a lead （）.

A．directs a delay in the successor activity

B．could be accomplished by a finish to-start relationship with a delay time

C．means the successor activity cannot start until after the predecessor is completed

D．allows an acceleration of the successor activity

采用高强度螺栓拼接的型钢构件，当连接处型钢斜面斜度大于（）时，应在斜面上采用斜垫板。

A、1/5

B、1/10

C、1/20