Parallel: have reduced....while raising

[freshy_cutie]

I found the problem from OG 12 (SC) that I don't understand, I know we cannot post the question so I'll just specify the number: p. 682 Q 134

I don't understand why a) is wrong, why "...<something> have reduced a, b, c and have raised d" is incorrect, since the <something> produces both effects?

Does it means that parallel must be only for the similar element as in goes in the same direction, if <something> causes sth to increase and sth else to decrease then we cannot use parallel construction???

[Ben Ku]

Sorry, even though you did not post the OG question, we are not allowed to discuss them on our forums. If you are in one of our classes, please ask OG questions during office hours or before/after class.