Three boys were enjoying themselves in their hometown of Bovina, Mississippi. However, their lives were turned upside down when they discovered the jawbone of a Mastodon(齿乳象).
Brothers Shawn and Caid Sellers and cousin Michael Mahalitc found the prehistoric bone in a piece of earth that was recently plowed(犁). “I thought it was a log,” Caid said. “I tried to pick it up and it was really heavy and I saw teeth on it.” The bone weighed about 50 pounds. They eventually got the bone to their home and fitted it in their tub(浴盆), but it took their collective strength, might and a golf cart, to carry the large Mastodon bone.
“They didn’t expect to find that,” Michael’s mom said. “Now that they have, I believe that they will be more aware of their surroundings and what they’re digging up when they are digging and playing.”
“We’ve gotten a lot of petrified(石化的) wood and Civil War relics from the area and that’s what I thought it was,” the brothers’ mother said. “This is our first set of teeth we’ve found. So we thought it was their imagination. We were quite surprised to see that it was not their imagination.”
They were exploring near the brothers’ home. Lo and behold(真想不到), they saw what they thought resembled a fossil. It was the curator of paleontology(古生物负责人) of the Mississippi Museum of Natural Science, George Phillips, who first identified the bone as a “very mature individual”.
The Mastodon was a mammal who lived during the prehistoric times. They had long tusks and trunks, like elephants. They were clearly different from their modern-day counterparts, as well as woolly mammoths(猛犸).
28. How did they find the jawbone of a Mastodon?
A. With great efforts. B. By chance.
C. Instructed by an expert. D. Through imagination.
29. At first the brothers’ mother thought the jawbone was________.
A. from people who died in the Civil War
B. the bone from a very mature individual
C. like a log or something
D. the prehistoric bone
30. The discovery of the jawbone of a Mastodon is important mainly because it ________.
A. helps people to know more about the Civil War
B. teaches kids to be more aware of their surroundings
C. promotes the research on more prehistoric creatures
D. attracts the Mississippi Museum of Natural Science
31. Which of the following can be the best title for the article?
A. Prehistoric Bones Recently Found in Mississippi
B. Not Petrified Wood Nor Civil War Relics
C. First Identifying Bone as a “Very Mature Individual”
D. Unexpectedly Discovering Mastodon Jawbone  28-31 BACD
 本文是一篇记叙文，美国密西西比的三个男孩在玩耍的时候无意中发现了齿乳象的颚骨，起初他们并不知道这是史前生物的遗骸，所发现的遗骸对史前生物的研究有所帮助。
28.推理判断题。根据第一段可知他们是在玩耍的时候无意中发现齿乳象的颚骨的。故B项正确。
29.判断推理题。根据第四段第一句 “We’ve gotten a lot of petrified wood and Civil War relics from the area and that’s what I thought it was,” the brothers’ mother said可知之前他们曾经发现过一些石化的木材以及内战时的遗物，所以他的母亲认为这次他们发现的还是内战里死亡的人的遗物。故A项正确。
30.推理判断题。根据倒数第二段最后一句和最后一段The Mastodon was a mammal who lived during the prehistoric times可推断，齿乳象的颚骨的发现对史前生物的研究有所帮助。故C项正确。
31.主旨大意题。本文是一篇记叙文，美国密西西比的三个男孩在玩耍的时候无意中发现了史前巨物齿乳象的颚骨，起初他们并不知道这是史前生物的遗骸。故D项正确。