Affirmative sentences in the simple present and simple past tense do not have an auxiliary verb. We use do, does or did to change them into questions.

Note that do and does are used in the present tense. Do is used with plural nouns and the pronouns I, we, they and you. Does is used with singular nouns and the pronouns he, she and it.

Did is used in the past tense with both singular and plural nouns and pronouns. Study the examples given below.

• Susie writes plays for television.

This statement is in the simple present tense and it doesn’t have an auxiliary verb. When we change this statement into a question, we use does as the first word. Note that we use does because the subject is a third person singular pronoun.

• Does Susie write plays for television? (NOT Does Susie writes plays for television?)
• Mike likes ice-cream. (Statement)
• Does Mike like ice-cream?
• He and his sister live in the same city. (Statement)
• Do he and his sister live in the same city? (Question)

Here we use do because the subject is plural.

• I like Shaw. (Statement)
• Do you like Shaw? (Question)
• I liked the movie. (Statement)

This statement is in the simple past tense. When we change it into a question, we use did as the first word. Note that did is used with both singular and plural nouns and pronouns.

• Did you like the movie? (Question) (NOT Did you liked the movie?) Did + like = liked