Submersibles that dive deeper are ( ).
A. larger in shape
B. smaller in shape
C. greater in quantity
D. smaller in quantity
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In ____, the earliest extant was printed.
A. 868A.D.
B. 1150A.D.
C. 612A.D.
D. 121A.D.
The invention of compass provided conditions for____.
Wood block printing was invented in ____and began to be widely used in ____.
FAST (Five-hundred-meter Aperture Spherical Telescope ) Tianyan was proposed by Chinese astronomer ____in ____and was completed in ____years.