Question

John tells you that his mother is in hospital.

You ask him: (how long / be / in the hospital?)

• A. How long will your mother be in the hospital?
• B. How long was your mother in the hospital?
• C. How long has your mother been in the hospital?
  
• D. How long have your mother been in the hospital?

Answer 1

The correct option is C How long has your mother been in the hospital?

The present perfect tense is used to describe something that happened in the past, but the exact time it happened is not important. It has a relationship with the present.

Have/has + past participle makes the present perfect.

In this sentence, a mention has been made about something which has happened in the past. Now since, the whole sentence is in the third person, we would be using "has" and not "have".

("have" is used in case of first and second person framed sentences.)

Now, for the past participle, it the form of a verb, typically ending in -ed in English, which is used in forming perfect and passive tenses and sometimes as an adjective. In this case the past becomes, "been"

Option C is correct.