Not all memories are sweet. Some people spend all their lives trying to forget bad experiences. Violence and traffic accidents can leave people with terrible physical and emotional scars. Often they relive these experiences.
Now American researchers think they are close to developing a pill, which help people forget bad memories. The pill is designed to be taken immediately after a frightening experience. They hope it might reduce, or possibly erase the effect of painful memories.
In November, experts tested a drug on people in the US and France. The drug stops the body releasing chemicals that fix memories in the brain. So far, the research has suggested that only the emotional effects of memories may be reduced, not that the memories are erased.
The research has caused a great deal of argument. Some think it is a bad idea, while others support it. Supporters say it could lead to pills that prevent or treat soldiers’ troubling memories after wars.
They say that there are many people who suffer from terrible memories. “Some memories can ruin people’s lives. They come back to you when you don’t want to have them in a daydream or nightmare. They usually come with very painful emotions,” said Roger Pitman, a professor of psychiatry(精神病学)at Harvard Medical School. “This could relieve（减轻）a lot of that suffering.”
But those who are against the research say that changing memories is very dangerous because memories give us our identity. They also help us avoid the mistakes in the past. “All of us can think of bad events in our lives that were horrible at the time but make us who we are. I am not sure we’d want to wipe those memories out.” said Rebecca Dresser, a medical ethicist.
What’s the main idea of this passage?

A．People often suffer from bad memories.

B．American researchers are trying to develop a pill.

C．Forget bad memories , and be happy.

D．The research has caused a heated argument.

The underlined word “it” in Paragraph 4 refers to “_____”.

A．the new drug

B．the research into the drug

C．the bad memory

D．the chemical in the drug

Which of the following is NOT the opinion of the opponents(反对者)?

A．Our memories give us our identity.

B．The memories help human avoid mistakes of the past.

C．The drug should be used in only very serious cases.

D．People may not be sure whether they want to wipe the memories out.