GWD TN 15 SC41 求解

41. GWD21-Q41:

The Environmental
Protection Agency’s proposal to place restrictions on both diesel fuel and diesel
engines has sparked a counterattack by the oil industry, saying that the
move will exacerbate
the nation’s fuel supply problems.

A.     
on both diesel fuel and diesel engines has sparked a
counterattack by the oil industry, saying

B.     
on both diesel fuel and engines have sparked the oil
industry to counterattack, and they say

C.     
on both diesel fuel and diesel engines has sparked a
counterattack by the oil industry, which says

D.     
both on diesel fuel and engines has sparked the oil
industry to a counterattack, saying

E.      
both on diesel fuel and diesel engines have sparked the oil
industry to counterattack, and it says

答案是C，求教A和C的区别是什么?各自在什么情况下使用