阅读下列短文，从每题所给的四个选项(A、B、C和D)中选出最佳选项。
We may all have had the embarrassing moment：Getting halfway through a story only to realize that we've told this exact tale before，to the person we're boring with it now. Why do we make such memory mistakes?
According to a research published in Psychological Science，it may have to do with the way our brains process different types of memory.
Researchers Nigel Gopie，of the Rotman Research Institute in Toronto，and Colin Macleod，of the University of Waterloo，divided memory into two kinds. The first was source memory，or the ability to keep track of where information is coming from. The second was destination memory，or the ability to recall who we have given information to.
They found that source memory functions better than destination memory，in part because of the direction in which that information is travelling.
To study the differences between source and destination memory，the researchers did an experiment on 60 university students，according to a New York Times report. The students were asked to associate 50 random(随意的) facts with the faces of 50 famous people. Half of the students “told” each fact to one of the faces，reading it aloud when the celebrity's picture appeared on a computer screen. The other half read each fact silently and saw a different celebrity picture afterward.
When later asked to recall which facts went with which faces，the students who were giving information out (destination memory) scored about 16 percent lower on memory performance compared with the students receiving information(source memory)．
The researchers concluded that outgoing information was less associated with its environmental context(背景)－that is，the person－than was incoming information.
This makes sense given what is known about attention. A person who is giving information，even little facts，will devote some mental resources to thinking about what is being said. Because our attention is finite(有限的)，we give less attention to the person we are giving information to.
After a second experiment with another group of 40 students，the researchers concluded that selffocus is another factor that undermines destination memory.
They asked half the students to continue giving out random information，while the other told things about themselves. This time around，those who were talking about themselves did 15 percent worse than those giving random information.
“When you start telling these personal facts compared with nonself facts，suddenly destination memory goes down more，suggesting that it is the selffocus component(成分) that's reducing the memory，”Gopie told Live Science.
The point of this article is to ________.

A．give advice on how to improve memory

B．say what causes the memory to worsen

C．explain why we repeat stories to the same person

D．introduce different kinds of memories

Those who read each fact silently and saw a different celebrity picture afterward ______.

A．can memorize more information

B．have worse memory

C．are more likely to repeat stories

D．paid more attention to themselves

The person who is giving information ________.

A．may receive little facts

B．focuses more on what he is saying

C．has finite attention

D．pays much attention to his own behavior

The underlined word “undermines” probably means ________.

A．weakens

B．benefits

C．explains

D．supports

What did the scientists conclude from the second experiment?

A．Destination memory is weaker than source memory.

B．Focusing attention on oneself leads to relatively poor source memory performance.

C．Associating personal experience with information helps people memorize better.

D．Selffocus is responsible for giving information twice or more to the same person.