【单选题】

The advantages of ’’an after the act’’ operation is:(31)____________(32)____________(33)_____________easilyOnly (34)____________of large firms and (35) _____________of small firms have a standard raw material inspection procedure.This testing of a product’’s effect must assess the impact of both ( 36 ) ____________and (37) ____________.

A、individual trade.
B．industry associations.
C．both
A、andB