C．It was built for trading in Southern China.

　　D．It enjoyed greater popularity than the "Silk Road"．

　　解析：选A　细节理解题。由第二段"Historians have traced the origins of the 'Tea Horse Road' back to the Tang dynasty ..."可知，茶马古道是从唐朝时开始的。

　　5．Where is the starting point of the "Tea Horse Road"？

　　A．Tibet. B．Beijing.

　　C．Pu'er County. D．Europe.

　　解析：选C　细节理解题。由第三段"...but a network of routes spreading out of Yunnan's Pu'er County."可知，茶马古道的起点是中国云南的普洱县。

　　6．The "Tea Horse Road" is now most popular with ________.

　　A．businessmen B．explorers

　　C．historians D．tourists

　　解析：选D　细节理解题。由最后一段"Today, the 'Tea Horse Road' is a hot spot for tourists."可知，茶马古道现在是深受旅游者青睐的景点。

　　C

　　If you need one more reason to be thankful, here it is.

　　One recent study from the University of California San Diego's School of Medicine found that people who were more grateful actually had better heart health."They showed better well­being, a less depressed mood, less tiredness and they slept better，" said the study's author, Paul J．Mills.

　　Researchers at the universities of Utah and Kentucky observed that stressed­out law students who characterized themselves as optimistic actually had more disease­fighting cells (细胞) in their bodies.

　　Robert Emmons, a professor at UC Davis, said there's even more evidence.People who keep a gratitude journal have a reduced fat intake - as much as 25 percent lower.Stress hormones (激素) like cortisol are 23 percent lower in grateful people.And having a daily gratitude practice could actually reduce the effects of aging to the brain.

　　"Being thankful has such a big effect because of the feelings that go along with it，"Emmons said."Gratitude works because it recruits other positive emotions (情绪) that have direct physical benefits."Research shows that when we think about what we appreciate, the calming part of the nervous system works and that can have protective benefits on the body.

"Some people may not be grateful by nature but it is a habit you can get used to，"said Dr.Norman Rosenthal, a doctor and author of Winter Blues."One very good way is being aware of comparing up.It almost always leads to unhappiness because you can always find a person who is more advantaged than you are."