The nurse is interviewing a client who is currently under the influence of a controlled substance and shows signs of becoming agitated. What should the nurse do（）

A. Use confrontation.

B. Express disgust with the client’s behavior.

C. Be aware of hospital security.

D. Communicate a scolding attitude to intimidate the client.

如图所示，取一个盛满水的杯子，用纸片把杯口盖严，再用手按住纸片把杯子倒过来，杯子里的水不往外流。实验说明：_______的存在。