Question

I think it's A

Which of the following sentences is correct?

I stayed up all night doing homework; however, I just couldn't concentrate.
I stayed up all night doing homework, however I just couldn't concentrate.
I stayed up all night doing homework however, I just couldn't concentrate.
I stayed up all night doing homework, however. I just couldn't concentrate.

Answer 1

you are awesome,the answer is A

Answer 2

You're correct. The answer is A.