When who or what asks about the subject, the question looks just like a statement: Who called? When it asks about the object, you need do, does or did: Who did you call? This small difference changes the meaning completely.
The pattern
Who called you?
Who did you call?
Who are you talking to?
01Object questions: use do, does or did
In most questions, who or what is the object: the person or thing that receives the action. Someone else is the subject, so you need a helper: question word + do/does/did + subject + verb.
Statement: Sara called her landlord. Question: Who did Sara call?
- What did you order?
- Who does your brother work for?
- What do you want for your birthday?
02Subject questions: no do
When who or what is the subject, it simply takes the subject's place. There's no do, does or did, and the verb keeps its normal form. In the present, add -s, because who and what are singular: Who lives here?
Statement: Someone called Sara. Question: Who called Sara?
- Who lives in the apartment upstairs?
- What happened at the meeting?
- Who took my charger?
- What makes you nervous?
| Subject question | Object question |
|---|---|
| Who called Sara? (Her landlord did.) | Who did Sara call? (She called her landlord.) |
| What broke? (The printer broke.) | What did you break? (I broke a glass.) |
| Who loves Jake? (Emma does.) | Who does Jake love? (He loves Emma.) |
03Which, whose, how many + noun
The same rule works with which, whose, what and how many followed by a noun. If the whole phrase is the subject, don't use do. If it's the object, use do.
- Which bus goes to the airport? (subject)
- Which bus do you take? (object)
- How many people came to the party? (subject)
- How many people did you invite? (object)
- Whose phone is ringing? (subject)
04Prepositions go at the end
When the question word is the object of a preposition, everyday American English puts the preposition at the end: Who are you talking to? What are you worried about? Starting with the preposition (About what...?) sounds stiff and formal.
Whom (To whom...?) is used mostly in formal writing. In conversation, Americans just say who.
- Where are you from?
- Who did you go to the concert with?
- What is this cable for?
- Which apartment do you live in?
05Common mistakes
Who did call you?
Who called you?
Who is the subject, so don't use did.
What did happen at work?
What happened at work?
What is the subject of happen, so no did.
Who you met at the party?
Who did you meet at the party?
Who is the object, so you need did before the subject.
With who are you going?
Who are you going with?
In natural English, the preposition goes at the end.