阅读理解We have most friends at the age of 26 after having spent the first quarter of our lives building

　
研究表明，我们在26岁时拥有最多的朋友，但是随着时间的推移，我们的朋友会减少。
46．How many friends can a 20­year­old college student make via Facebook?
A．4.　　　　　　　　　 B．12.
C．18. D．22.
B　解析：细节理解题。根据第四段最后一句中的“via Facebook，compared to 18 to 24­year­olds who make 12”可知，通过脸书网年龄在18到24岁的人可以交到12个朋友，故B项正确。
47．In Paragraph 5, the author is trying to tell the readers ________．　
A．how important making friends is
B．that friendship is not easy to keep
C．how much has been done to keep friendship
D．that friendship at school is important
D　解析：细节理解题。根据第五段Sam Owen所讲的话的第二句“It is a key time in our lives when friendship is growing through sharing notes，giving gifts，seeing each other regularly and laughing a lot.”可知，学校时光是人生中建立友谊的重要阶段，这时候的友谊成长于分享笔记、赠送礼物、互相探望、一起欢笑中，故D项正确。
48．The underlined phrase “drift away from” in Paragraph 6 means “________”．
A．make sense of B．lose contact with
C．feel sorry for D．make up with
B　解析：词义猜测题。根据第六段中的“Over half of us lose friendship...apart from close pals.”及画线词所在句“Having children also causes 19% to...childhood friends.”可以判断，画线词意为“失去联系”，故B项正确。A项意为“理解”，C项意为“对……感到抱歉”，D项意为“与……和好”，都与语境不符。

49.What’s the main idea of this passage?
A. When we have most friends               B. How to maintain friendship
C.  Why we should make friends              D. Where we can meet our closest friends
A　解析：主旨大意题。根据首段“研究表明，我们在26岁时拥有最多的朋友”故A项正确。其他段落主要用来解释和说明这个研究发现，所以B、C、D以偏概全。
50．This passage is most probably taken from ________．
A．Facebook or Twitter B．an advertisement
C．a textbook D．a newspaper
D　解析：文章出处题。根据第一段中的“a new research has claimed”以及最后一段中的“these days”，再结合选项可以判断，本文最可能摘自报纸，故D项正确。