求问一道题，各位大牛请帮忙~~

57. 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

The answer is C,but how about A?

what is the difference between saying and which says?