I am not sure of the answer which one of the option is it?

Step-by-step explanation:
well, there are a few things you have to burn into your brain for all times. one of these is : the sum of all angles in a triangle is always 180 degrees. it does not matter what type of triangle it is. the sum is always 180 degrees.
so,
180 = A + 80 + 40
60 degrees = A
so, B. is the right answer.