If the fire alarm is sounded, all residents are requested to ______ in the courtyard.

A．voodoo prevails more in Africa than in other pans of the world
B．the sudden deaths of animals differ in causes from those of people
C．the connection between sympathetic nervous system and irregular heart rhythms is clear
D．In modern society, sudden deaths take place much less because of higher medical levels

A．mental stress
B．physical diseases
C．unexpected accidents
D．poisons