A is correct.
Explanation: Because it's means it is
Its means something like theirs, itself, e.x - the dog likes to curl up in its bed.
So 1040 out of 2600 means 1040/2600=104/260=26/65
percent means part out of 100
so x%=x/100
so 26/65 is equal to x/100
26/65=x/100
multiply both sides by 100
2600/65=x
simplify
2600/65=40=x
answer is 40%
Yes, it's a dependent clause.