国际上流行的视频制式标准为有NTSC、PAL、VGA三种制式。()
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风扇皮带过松或沾有油污打滑，将引起发电机不发电。()
It is implied in the last two paragraphs that______.
A. the acidification is an indicator of the declines of the ocean
B. humans should harmonize their activity with the laws of nature
C. climate change has endangered many marine creatures
D. most energy for future development can be obtained from the sea
What can we infer from Paragraph 1？
A. Ocean exploration has made little progress so far.
B. Deep parts of the solar system should be studied.
C. More work is needed for a better use of marine resources.
D. Submersibles can hardly reach as deep as one mile underwater.
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