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?