Thediscoveryofanancientgiantpandaskullhasconfirmeditsbamboodietdatesbackmorethan2millionyearsandmayhaveplayedakeypartinitssurvival．AChinese-USresearchteamreportsitsresultstodayfollowingstudiesonafossilskul

Question

The discovery of an ancient giant panda skull has confirmed its bamboo diet dates back more than 2 million years and may have played a key part in its survival．
A  Chinese-US research team reports its results today following studies on a fossil skull found in south China's Cuangxi Zhuang Autonomous Region in 2001．
The six fossils unearthed in Jinyin Cave are dated between 2.4 and 2 million years ago，according to the report in Proceedings of the National Academy of Sciences，an influential US journal．
Jin Changzhu，of the chinese Academy of Sciences （CAS） and lead author of the paper，said the smaller fossil skull indicates the giant pandas were about a third smaller than today's pandas．
Researchers knew the panda reached its maximum size about 500，000 years ago，when it peaked，and then gradually became smaller．
Jin，a paleontologist （古生物学者） at the Institute of Vertebrate paleontology and Paleoanthropology （古人类学） attached to the CAS，said the size variation was a basic rule of evolution．
"A species tends to grow bigger when it reaches the peak of its population，but becomes smaller when numbers decline，"he said．
The dental remains of the skull，which is the oldest giant panda skull ever found，are similar to today's pandas，indicating the type of teeth that could munch （津津有味地嚼）mountains of bamboo．A panda can eat up to 40kg of bamboo per day．
Paleoanthropologist Russell Ciochon，the US co-author at the University of lowa，said the panda's focus on bamboo could have helped it survive all these years．
"Once an animal begins to rely on a common and stable food source，such as bamboo，it tends to evolve a larger body size，"he said．"As individuals of the evolving species grow bigger，they have a better chance not to be eaten by predators （肉食动物） due to their larger body size．"
33．According to the research of the CAS，there were most pandas in the world___．
A.2 million years ago
B．between 2.4 and 2 million years ago
C.500，000 years ago
D．Nowadays
34．The underlined word"variation"in para 6 means___．
A．fall           B．change       C．increase       D．decrease
35．From the passage，we can learn___．
A．pandas began to eat bamboo 2 million years ago
B．a species tends to grow smaller when numbers decline
C．the giant pandas were about a third the size of today's pandas
D．pandas'bamboo has played an important role in its development．

Answer 1

33．C．事实细节题．根据短文Researchers knew the panda reached its maximum size about 500，000 years ago，when it peaked，and then gradually became smaller．可知500，000年以前的大熊猫数量是最多的，故选C．
34．B．词义猜测题．根据下文"A species tends to grow bigger when it reaches the peak of its population，but becomes smaller when numbers decline，"he said．可知，一个物种的数量达到顶峰，它们的体型会变大，数量减少，体积会变小，所以是体型的改变，故选B．
35．B．事实细节题．根据短文"A species tends to grow bigger when it reaches the peak of its population，but becomes smaller when numbers decline，"he said．可知当一个物种数量减少时，这个物种的生物的体型会变小，故选B．