The researchers have conducted an experiment to prove that people will act in emergencies when ______.

A．When a person tries to help others, he must be clear that there is a real emergency.
B．When a person tries to help others, he should know whether they are worth his help.
C．A person must take the full responsibility for the safety of those in emergencies if he wants to help.
D．A person with a heart attack needs help.

A．we shouldn't blame a person if he fails to act in emergencies
B．a person must feel guilty if he fails to help
C．people should be responsible for themselves in emergencies
D．when you are in trouble, people will help you anyway