The word them in the passage refers to
A. less-developed nations.
B. individuals.
C. bonds.
D. primary groups.
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Why does the professor say this:
A. To praise the area's beautiful winter scenery
B. To persuade students to build their own homes
C. To describe the most common one of limestone
D. To explain why so many snakes live in the region
How do the garter snakes deal with seasonal variations in temperature？
A. They grow an extra layer of skin in winter and shed it in summer.
B. They survive by migrating toward the south every winter.
C. They move into the limestone pits to escape winter temperatures.
D. They vary their food intake to maintain a constant body temperature.
The word secretes in the passage is closest in meaning to
A. produces.
B. allows.
C. contains.
D. transforms.
Listen again to part of the lecture．Then answer the question. Why does the professor say this:
A. To describe the shape of the arch
B. To define the concept of lateral thrust
C. To compare two types of physical force
D. To explain why arches must be large
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