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

我国某市有两家大型有色金属冶炼厂，近年该市也多次发生酸雾事件，从城市发展的角度看，该市准备采取的一些措施中最合理的是

A．对金属冶炼厂实行关停并转

B．增加化学设备，通过化学手段消除废气中的SO₂

C．在有色金属冶炼厂附近办硫酸厂，回收利用废气中的SO₂

D．缩小工厂生产规模，控制废气排放量