17.
A. The willingness to offer timely help
B. The joy found in each other’s company
C. Personal bonds
D. Emotional factors
18.
A. Failure to keep a promise
B. Lack of frankness
C. Feelings of betrayal
D. Loss of contact
19.[音频]
Along the low-lying Colorado River
B. At the Dinosaur National Monument
C. Along the border of the U.and Canada
D. At museums of natural history in large cities
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
微信支付 
支付宝支付