单项选择题

"The horizons of science have expanded" means that ______.

A．the horizon changes its size from year to year
B．science has developed more fields of endeavor
C．scientists have made great progress in studying the horizon
D．scientists can see further out into space
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单项选择题
The example given in the passage illustrates how ______.
A．pure science operates independently of applied science
B．the applied scientist discovers the basic laws of nature
C．applied science defines all the areas in which basic research is done
D．applied science suggests problems for the basic scientist
单项选择题
The problem discussed in the second paragraph called for ______.
A．selecting the best hear-resistant metal from existing metals
B．developing a turbine wheel capable of generating hear up to 1, 600 degrees Fahrenheit
C．developing metals and alloys that would withstand terrific temperatures
D．causing the jet engine to operate at higher temperatures
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