The best topic for the passage is "_________".
A. What Is a Telescope
B. The History of Telescopes
C. How a Telescope Works
D. How Far a Telescope Can Reach
He hopes he can visit the United Nations building while he ____________ in New York next summer.
A. has been
B. is
C. will be
D. shall be
The writer talks mostly about pictures taken _________.
A. outdoors
B. indoors
C. in color
D. for newspapers
设f(x)满足f"(x)+(f'(x))2=x且f'(0)=0，则 ( )
A. f(0)是f(x)的极大值
B. f(0)是f(x)的极小值
C. f(0)不是f(x)的极值，(0,f(0))是曲线y=f(x)的拐点
D. f(0)不是f(x)的极值，(0,f(0))也不是曲线y=f(x)的拐点
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