The specific analysis method is
Extended OB Because OA =OB= OC, so ∠ABO=∠ BAO.
After the generalization of ∠OBC =∠OCB, the theorem of triangle interior angle sum is used
Because ∠ ABC = ∠ ADC = 70, ∠AOC = 140, and the sum of quadrilateral internal angles is 360, we use 360-70- 140= 150.
So the answer is d.
Do you understand my solution?