Answer:
B (a=60, b=120)
Explanation:
1. m∠AOB = 180°
2. Since the ratio of a to b is 1:2, set the measure of a as x, and the measure of b as 2x.
3. a+b = 180, so x+2x = 180, 3x = 180, x = 60
4. x = a, so if x=60, then a = 60
5. if b=2x, then b = 2a, which is 2*60 = 120
Hope this helps