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.

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

The above statement has one misspelled word grammer, and a fragment sentence. The first sentence is in continuation so full stop is replaced by a comma. There are also 2 comma errors. The corrected and revised statement is given below,

When proofreading for grammar 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.