English verbs that describe an action, rather than an occurrence or a state of being, are the most common kind of verbs. Unlike the other kinds of verbs, they have the common feature of always ending in the letter "s" in the present tense third person singular form:
He takes a step back.
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He eats the fruit.
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He (subject) takes (action verb) a step (object).
He (subject) eats (action verb) the fruit (object).
To change the above affirmative sentences to negative sentences, add the verb "to do" and "not," the declarative form of "no."
He does not take a step.
He does not eat the fruit.
To change the affirmative form to the interrogatory form (or question), add the verb "to do" at the beginning of the sentence with a question mark at the end:
Does he take a step?
Does he eat the fruit?
So to reiterate:
Affirmative: He takes a step.
Negative: He does not take a step.
Interrogatory: Does he take a step?
Affirmative: He eats the fruit.
Negative: He does not eat the fruit.
Interrogatory: Does he eat the fruit?
Browse some videos at Yabla English and find some other examples of affirmative sentences with action verbs. Practice turning them into negative sentences with "to do" and "not", and changing them into interrogative sentences with "to do" and a question mark.