32. ___
A. They defend the bone against viruses.
B. They prevent oxygen from entering the bone.
C. They break down bone tissue.
D. They connect the bone to muscle tissue.
33. ___
A. They have difficulty identifying these cells.
B. They aren't sure how these cells work.
C. They've learned how to reproduce these cells.
D. They've found similar cells in other species.
34. ___
A. To learn how to prevent a bone disease.
B. To understand differences between bone tissue and other tissue.
C. To find out how specialized bone cells have evolved.
D. To create artificial bone tissue.
35. ___
A new fuel for buses.
B. The causes of air pollution.
C. A way to improve fuel efficiency in buses.
D. Careers in environmental engineering.
31. ___
A. The strength of ocean currents.
B. The movement of sediment deep in the ocean.
C. The best methods for studying deep ocean processes.
D. A new way of measuring the depth of the ocean.
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