【单选题】

Questions 14 to 17 are based on the following passage.At the end of the passage, you will be given 20 seconds to answer the questions.

Now, listen to the passage.
Dr. Sheeler was surprised at Mr. Nelson’s call becauseA．the new patient should not have known his phone number.
B．he seldom called at night.
C．the Nelsons had been very healthy.
D．the Nelsons had not called him for a long time.