联系用的手信号中，（）的显示方式，夜间为白色灯光左右小摇动。

A、过标信号

B、互检信号

C、溜放信号

D、停留车位置信号

After 5 days of hospitalization, the client who is receiving morphine sulfate for pain control asks for more pain medication with increasing frequency and exhibits increased anxiety and restlessness. His physical condition is stable. What is the probable cause of his behavior（）

A. His morphine dosage is too high.

B. His coping mechanisms are exhausted.

C. He is becoming addicted to the narcotic.

D. He has developed tolerance to his narcotic dosage.