studies/ is studying/ has been studying for a year

[joham]

Cathy is taking notes of the grammatical rules in class at Sunshine School, where she ______ English for a year.
This was one of China's university admission examination questions. The given answer is: "has been studying".

I know the given answer is right. But I thought another two of the four choices were right too:
studies: if this is what is arranged in the teaching program. And
is studying: if this is what Cathy has arranged and she's just starting the course.

Could I ask native English teachers to help me?
Thank you very much.

[Dawood Usmani]

Cathy is taking notes of the grammatical rules in class at Sunshine School, where she ______ English for a year.
This was one of China's university admission examination questions. The given answer is: "has been studying".

I know the given answer is right. But I thought another two of the four choices were right too:
studies: if this is what is arranged in the teaching program. And
is studying: if this is what Cathy has arranged and she's just starting the course.

Could I ask native English teachers to help me?
Thank you very much.

The first sentence is in present simple which indicates that the second sentence should be in present perfect continuous. The act of taking notes is being done (at the time of speaking) by Cathy. This means she is already there studying. Now, the question rises how long she has been studying there. That (the second sentence) is the answer to this question. The concept is quite clear I suppose but still wait for some native speakers's replies.
Regards!
Dawood