For questions we generally use the aux verb ‘do’. Also with who, what, how many etc.

When answering Wh- Questions we cannot reply with „yes“ or „no“. 

 

When we are asking a question to find out who or what was the object of a situation we use the auxillary verb DO.

 

Information sentence	Question sentence
Kate spoke to somebody. Somebody is the object of the sentence.	Who did Kate speak to? We use the auxilary verb (do) in the past tense.

When we are asking a question to find out who or what was the subject of a situation we do not use the auxillary verb do.

 

Information sentence	Question sentence
Somebody spoke to Kate. somebody is the subject.	Who spoke to Kate? Note, We do not use the auxilary verb DO.

Who does want something to drink? incorrect

Who wants something to drink? correct

Who is the subject

 

How many people did go skiing with you? incorrect

How many people went skiing with you? correct

People is the subject

 

Which train does go to London? incorrect

Which train goes to London? correct