Answer: Option
C
Explanation:
Given that,

1 
∠A + 
1 
∠C + 
1 
∠B = 80° ⇒ 3∠A + 2∠C + 3∠B = 480° 
2 
3 
2 
⇒ 3(∠A + ∠B) + 2∠C = 480° ....(i)
Also, in ΔABC,
∠A + ∠B + ∠C = 180°
On multiplying both sides L.H.S. & R.H.S. by 3, we get
3(∠A + ∠B) + 3∠C = 540° ..... (ii)
On subtracting Eq. (i) from Eq. (ii), we get
∠C = 60°.