Answer:
A.
Step-by-step explanation:
The Six Traits of Writing Model is a model helpful in writing a good prose. The Model is a result of research for many years. The model consists of six traits that are essential to make any writing successful. They are ideas, organization, voice, word choice, sentence fluency, and conventions.
In the given case, the students are proofing their papers are at the sixth trait of the model, that is conventions.
Conventions include proofreading of the work. It is a mechanical trait in the writing process as it involves making the writing more correct grammatically, in spelling, punctuation, paragraphing, and capitalization. Since the students are proofing their papers they are in the sixth part of the model.
Thus, option A is correct.