GMAT Sentence Correction (SC) | Re: While some propose to combat widespread illegal copying of

While some propose to combat widespread illegal copying of computer programs by attempting to change people's attitudes toward pirating, othersby 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: In this complex sentence , the main clause is missing; Hence this is a fragment