The answer is C but I don't like this answer and I will tell you why.
To get this answer your took the measure of 8 and multiplied by 1.5 to get 12 and the measure of 10 and multiplied by 1.5 and got 15. So the answer C is 12 x 15.
I would have normally taken the original measurement of 8x10 = 80 and multiplied that by 1.5 yielding 120 inches sq area and this is not what you get when you multiply 12 x 15, which is instead 180.
The question is ambiguous regarding how we are increasing the size, interested to hear what your teacher says about the answer.
Since 120 is not one of the solutions it is clear they are looking for 180 which is answer C.
All the best