16.[音频]
A. Similarity in interests
B. Mental stimulation
C. Openness
D. Compassion
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
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