Answer:
D. 80 is your answer
Explanation:
If ∠6 is 120 and ∠5 is 100 we see a pattern forming for example, if we divide 120 by 6 we get 20 this is the same for if we divide 100 by 5, we get 20. Now all we need to do for ∠4 is to multiply it by 20 = 80, which is your answer!
Have a great day and I hope this helps!