Question

Writers editing sentences for errors in grammar and usage would look for
a. ways to replace overused words.
b. problems with verb tenses.
c. sentences missing commas or periods.
d. misused or missing capitalization.

Answer 1

When a writer edits his/her own work, all four errors in grammar and usage listed above, need to be looked for.
a. Ways to replace overused words.  A paragraph sounds clumsy when the same words are used too many times in a sentence/paragraph
b. Problems with verb tenses. It is very important to use the same verb tense throughout your written work. 
c. Sentences missing commas and periods. If a sentence does not contain commas and periods, it is confusing and ends up being a jumble of words. 
d. Misused or missing capitalization.

Answer 2

ANSWER: B. problems with verb tenses

When editing for errors in grammar and usage, a writer should primarily look at the grammatical structure of the sentences and any possible mistakes in the way some of the words are used.

Among the options, only choice B is about a grammar issue. The rest of the options are all about technicalities that do not concern grammar.