Choose the best answer to this question based on the information in Text A of Unit 4. 4. How many accredited centers for weight-loss surgery are there for teenagers in the U.S.A?

Choose the best answer to this question based on the information in Text A of Unit 4. 4. How many accredited centers for weight-loss surgery are there for teenagers in the U.S.A?
A.6.
B.850.
C.35.
D.33.
正确答案：6.