Explanation: When an action starts before and is still continuing in the present, the verb is in the present perfect continuous tense. But for verbs that don’t have a continuous form, when for/since is used, they are applied in the present perfect tense.

Structure of Present Perfect Continuous:
subject + have been/has been + (verb+ing)… since/for…

Generally, verbs like Be, Have, See, Know, etc. do not have a continuous form.

In the above sentence, the verb is be, and we know be verb does not have a continuous form.

Therefore, the correct answer here is “B. has been.”

So we thing you get answer of “She ( be ) unconscious since four O’clock.“. If you understand this rule you can answer this question. Answer this question in the comment box.

➡️Choose the correct sentence:

A) He has been doing his homework since morning.
B) He has been done his homework since morning.
C) He is done his homework since morning.
D) He has done his homework since morning.

If you don’t comment we think you can not understand.