Why did it take so long to develop the X-ray microscope
A. Funds for research were insufficient.
B. The source of illumination was not bright enough until recently.
C. Materials used to manufacture X-ray tubes were difficult to obtain.
D. X-ray microscopes were too complicated to operate.
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According to the passage, customers are attracted to a product because it appears to ______.
A. have a sufficiently attractive design
B. offer good value for money
C. fulfill the manufacturer's claims
D. satisfy their personal needs
The word "nudge" in the first sentence of paragraph six means ______.
A. progress
B. encouragement
C. push
D. growth
经济中由库存调整引起的周期被称为( )
A. 长周期
B. 中长周期
C. 主周期
D. 短周期
The pace of recycling will have to be artificially quickened because ______.
A. nature' s own pace is slowing down rapidly
B. the "working capital" of recycled material has all been used up
C. the earth' s resources cannot be replaced by man
D. the earth' s growing population requires more and more resources
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