When proofreading for grammer errors. First locate the subject of the sentence. Then, you should double-check the agreement of nouns and antecedents as well as the agreement of subject and predicate. The grammar check on the computer may be helpful, but should not replace manual proofreading.

This selection has two misspelled words, one comma splice, and one fragment.
This selection is correct without any revisions,
This selection has a misspelled word, one sentence fragment, and one comma error. replace manual proofreading.
This selection has two misspelled words, one comma splice, and one fragment.
This selection is correct without any revisions.
This selection has a misspelled word, one sentence fragment, and one comma error.