治安行政处罚，是公安机关对于不履行治安法规所确定的义务或者危及社会治安秩序，情节轻微，尚不够刑事处罚的行为，依据治安管理法规的规定实施的行政处罚。 ( )

Textile business has become more and more difficult（）the competition grew.

A．as

B．befor

C．since

D．after