https://gmatclub.com/forum/while-some-propose-to-combat-widespread-illegal-copying-of-computer-151395.html
While some propose to combat widespread illegal copying of computer programs by attempting to change people's attitudes toward pirating, others
by suggesting reducing software prices to decrease the incentive for pirating, and still others by calling for the prosecution of those who copy software illegally.
(A) by suggesting reducing software prices to decrease the incentive for pirating, and still others by calling
(B) by suggesting the reduction of software prices to decrease the incentive for pirating, and still others call
(C) suggest the reduction of software prices for decreasing the incentive for pirating, and still others call
(D) suggest the reduction of software prices to decrease the incentive for pirating, and still others by calling
(E) suggest reducing software prices to decrease the incentive for pirating, and still others are calling
Ans E:
MGMAT's comments
While some propose to combat widespread illegal copying of computer programs by attempting to change people's attitudes toward pirating, others
by suggesting reducing software prices to decrease the incentive for pirating, and still others by calling for the prosecution of those who copy software illegally.
A)by suggesting reducing software prices to decrease the incentive for pirating, and still others by calling
B)by suggesting the reduction of software prices to decrease the incentive for pirating, and still others call
C)suggest the reduction of software prices for decreasing the incentive for pirating, and still others call
D)suggest the reduction of software prices to decrease the incentive for pirating, and still others by calling
E)suggest reducing software prices to decrease the incentive for pirating, and still others are calling
The parallel verbs are some PROPOSE (to combat), SUGGEST (reducing), and ARE CALLING (for X). All three verbs are in the present tense (although the third is in the present progressive, it's still considered present). If I could wave a wand, I would choose to make the third verb CALL, not ARE CALLING, but I don't have that option while retaining correct grammar in the rest of the sentence (e.g., in choice C, the expression "for decreasing" is definitely incorrect -- you must express the intended result of "reducing software prices" with an INFINITIVE such as "to decrease").