According to the passage, the invention of the visible - light microscope allowed scientists to ______.
A. see viruses directly
B. develop the electron microscope later on
C. understand more about the distribution of the chemical elements
D. discover single-celled plants anal animals they had never seen before
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Which of the following is NOT mentioned when the author explains the reasons of the rapid growing number of English speaker
A. New pupils are required to learn English at school.
B. Monolingual old people are encouraged to speak English.
C. Employees have to learn English if they want to get a chance of promotion.
D. Scholars use English as the language of their academic works more often than other languages.
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.
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
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