Which form of a regular verb is used with a third-person singular subject in…

Concept

In the simple present tense, a finite lexical verb agrees with its subject in person and number.

With a third-person singular subject, a regular verb normally takes the suffix -s or -es; other present-tense subjects use the base form.

Application

1. Identify the subject as third-person singular, such as he, she, it, or one singular noun.

2. Begin with the base form walk.

3. Add the regular third-person singular ending -s, producing walks.

Contrast

• walk is the base form used with I, you, we, they, and plural noun subjects in the simple present.

• walking is the -ing participle used with a form of be in progressive constructions.

• walked is the regular past and past-participle form.

• walks is the -s inflection used with he, she, it, or a singular noun subject in the simple present.

Cross-check

She walks to school is grammatical; changing the subject to They changes the verb to walk. This confirms the subject–verb agreement rule.

Therefore, the required form is walks.