20.
A. Volcanic explosions could bring whole animal species to extinction
B. Some natural disaster killed a whole herd of dinosaurs in the area
C. The pit should be carefully preserved for the study of dinosaurs
D. The whole region must have been struck by a devastating flood
21.
A. They floated down an eastward flowing river
B. They lay buried deep in the sand for millions of years
C. They skeletons of dinosaurs inhabiting the locality
D. They were remains of dinosaurs killed in a volcanic explosion
22.[音频]
A. Indulging in seeking leisure and material comfort
B. Attaching too much importance to independence
C. Failing to care for parents in the traditional way
D. Leaving their parents on the verge of starvation
23
A. They have great difficulty living by themselves
B. They have little hope of getting any family care
C. They have fond memories of their good old days
D. They have a sense of independence and autonomy
24
A. People in many parts of the world preferred small-sized families
B. There have been extended families in most parts of the world
C. Many elderly people were unwilling to take care of their grandchildren
D. So many young Americans refused to live together with their parents
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