I think it is study of English. Of course there are few important things.
For example, playing,club-activities and part-time-job.
But I came to learn English at this college.
So,I think it is most important things.
× I think it is study of English.
It が何を指すのか分からないため、
I think it is important to study English.や
I think the most important thing is study of English.
などと書き換えるといい。
