Question

You know that Jane is a good friend of Carol's.

You ask Jane: ___________. (how long / know / Carol?)

• A. How long do you know Carol?
• B. How long did you know Carol?
• C. How long have you known Carol?
• D. How long have you been knowing Carol?

Answer 1

The correct option is C How long have you known Carol?

The present perfect is a verb tense which is used to show that an action has taken place once or many times before now, here, knowing Carol. The present perfect is formed using has/have + past participle, here, "have known". Questions are indicated by inverting the subject and has/have. Hence, Option C is correct.

The rest of the options do not adhere to this condition.

Option A states a routine or habit, B states a past action, whereas the action 'to know Carol' hasn't stopped. Option D states a continuous action, but 'to know someone' is a short action, we don't use the continuous form 'knowing'.

Hence these options are incorrect.