4．Scientists have never known for sure whether dinosaurs were warm-blooded animals，like mammals and birds，or cold-blooded，like reptiles and fish．A re cent study shows that in fact many dinosaurs might not have belonged to either category but instead have fallen somewhere in the middle．
Warm-blooded animals ha ve bodies that are able to make their own heat．Their body temperatures stay about the same whether it is hot or cold outside．Cold-blooded animals can not make their own heat，so their body temperatures depend on how warm the outside temperature is．Warm-blooded animals have much more active lifestyles than cold-blooded ones．
When scientists first discovered the bones of ancient dinosaurs in the 1800s，they were sure the huge creatures must have been slow．But as scientists found more bones of smaller，quicker dinosaurs，like Velociraptor，they realized that the creatures may have been much more active than they had thought．
A team of biologists began to examine．They knew that warm-blooded animals grow faster than cold-blooded ones．The researcher realized that they could determine whether a dinosaur had been warm-or cold-blooded by finding its growth rate．
The scientists examine the growth rings in bones from 21 different dinosaur species．The width of the growth rings showed how much the dinosaurs grew each year，much like the rings in the tree trunk do．
"Our results showed that dinosaurs had growth rates th at were actually not characteristic of warm-blooded or cold-blooded animals，"said Brian Enquist，a scientist on the research team．"They didn't act like mammals or birds，nor did they act like reptiles or fish．"Instead，dinosaurs fell somewhere in between．Scientists called the middle-of-the-road creatures"mesotherms"．
Being mesotherms gave dinosaurs many advantages．They were faster and stronger than reptiles that had to rely on the sun for warmth．Being somewhat cold-blooded had its benefits too．Cold-blooded animals burn energy more slowly．So they need much less food to l ive than warm-blooded animals．"It is doubtful that a lion the size of T-rex could eat enough to survive，"explains John Grady，another biologist on the research team．By being mesothermic，the dinosaurs could be both fast and big．
12．What is Paragraph 2 mainly about？C
A．The advantage of cold-blooded animals．
B．The disadvantages of warm-blooded animals．
C．The differences between warm-and cold-blooded animals．
D．The advantages of both warm-and cold-blooded animals．
13．It can be inferred that mesotherms growD．
A．a(chǎn)s slowly as cold-blooded animals
B．a(chǎn)s fast as warm-blooded animals
C．slower than cold-blooded animals
D．slower than warm-blooded animals
14．A lion is mentioned in the last paragraph to stress thatD．
A．dinosaurs moved very fast
B．dinosaurs had to rely on the sun for warmth
C．dinosaurs are large animals
D．dinosaurs needed less food to survive
15．The text is mainly aboutC．
A．how dinosaurs disappeared
B．the growth areas of dinosaurs
C．whether dinosaurs were warm or cold-blooded animals
D．the appearance and behavior of dinosaurs．
分析 科學(xué)家一直都不確定恐龍到底是溫血還是冷血?jiǎng)游�，為此開(kāi)展了一些研究 和調(diào)查．
解答 CDDC
12．C 推理題．根據(jù)第二段的一些句子，如Warm-blooded animals ha ve bodies that are able to make their own heat以及Cold-blooded animals can not make their own heat，得知，主要比較冷血和溫血?jiǎng)游镏g的一些差別，故選C．
13．D 細(xì)節(jié)題．文章里They knew that warm-blooded animals grow faster than cold-blooded ones告訴我們溫血?jiǎng)游锉壤溲獎(jiǎng)游镩L(zhǎng)的速度更快，再接合最后一句dinosaurs fell somewhere in between．Scientists called the middle-of-the-road creatures"mesotherms"．故選D．
14．D 細(xì)節(jié)題．在文章中Cold-blooded animals burn energy more slowly．So they need much less food to l ive than warm-blooded animals得知，冷血?jiǎng)游锵哪芰烤徛运麄冃枰苌俚氖澄飦?lái)維持生存，獅子和恐龍都屬于這類動(dòng)物，故選D．
15．C 主旨題．根據(jù)文章第一段Scientists have never known for sure whether dinosaurs were warm-blooded animals，like mammals and birds，or cold-blooded，like reptiles and fish科學(xué)家一直都不確定恐龍到底是溫血還是冷血?jiǎng)游�，為此開(kāi)展了一些研究 和調(diào)查，所以整個(gè)文章大意為選項(xiàng)C．
點(diǎn)評(píng) 本文是一篇科教類閱讀，題目涉及多道細(xì)節(jié)理解題，推理判斷題，主旨大意題，詞義猜測(cè)題．做題時(shí)學(xué)生應(yīng)仔細(xì)閱讀原文，把握文章主要內(nèi)容，聯(lián)系文章上下文內(nèi)容并結(jié)合所給選項(xiàng)含義，從中選出正確答案，一定要做到有理有據(jù)，切忌胡亂猜測(cè)
