Question

I _____ doing this exercise. You can borrow my notebook now.​

Answer 1

Answer:

I am doing this exercise. You can borrow my notebook now.

Answer 2

Answer:

I am doing this exercise. You can borrow my notebook now.

Explanation:

'I' is an exception and we always use 'am' with with it. Only in some rare cases we might use some other helping verb but in this case am will come.