(A) in effect manufacturing its own antifreeze

(B) effectively manufacturing antifreeze of its own

(C) in effect manufacturing their own antifreeze

(D) so that they manufacture their own antifreeze

(E) thus the manufacture of its own antifreeze

C是正确答案,但是对于干扰项D,我不太清楚错在什么地方,看了注释也不是很清楚,望牛牛指教.

1）答案中so that多数错。2）D选项的they错，manufacture的主语是前面convert的过程，而不是动物。3）c 比d 简洁，ing形式表伴随情况。