The economists think the profit opportunities are rare because
A. the market is not efficient.
B. too many people go for it.
C. the prices are always fluctuating.
D. few people have the clear insights,
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How does the man feel about the development of tooth transplants？
A. Suspicious and angry.
B. Surprised but hopeful.
C. Doubtful and worded.
D. Shocked but moved.
The mining industry in the U.S. became safer after the late 1960s because
A. the U.S. Senate passed laws requiring federal mine inspections.
B. the U.S. Congress passed laws requiring federal mine inspections.
C. the U.S.health and safety officials passed laws requiring federal mine inspections.
D. the U.S. mine companies passed laws requiring federal mine inspections.
What is the speaker mainly talking about？
A. How animals survive harsh conditions in the wild.
B. How animals alter colors to match their surroundings.
C. How animals protect themselves against predators.
D. Flow animals learn to disguise themselves effectively.
The man is surprised at the fact that
A. the sound of drilling is painful.
B. the woman has to have her tooth refilled.
C. teeth cannot be transplanted.
D. people can transplant hearts.
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