What is the final result if trees are cut down ruthlessly？
A. The roots of trees will break up the soil and bind the soil together.
B. The rainwater falls on the ground will wash away the soil.
C. The rainwater will lead to floods and carry away the rich top-soil.
D. The whole farmland will become a large area of poor, sand-covered land.
A．fullB．fondC．proudD．out
A. full
B. fond
C. proud
D. out
A．hurtsB．effectsC．showsD．destroys
A. hurts
B. effects
C. shows
D. destroys
One of the differences between cross-sectional research and longitudinal research is that______.
A. the latter usually focuses on only one subject, while the former involves groups of subjects
B. the former can be free from the influence of social changes
C. the latter can be free from the influence of social changes
D. the former costs less money and takes less time
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