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Urgent: detailed answer to the ninth question in the mathematics examination paper of Wuhan City, Hubei Province in 2009.
The answer is D.

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?