The most significant source of man-made radiation exposure to the average person is from_____.

单选题

The most significant source of man-made radiation exposure to the average person is from_____.

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单选题

The most significant limitation of VHF signals is that they _______ ．

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单选题

Perhaps the most significant postwar trend was the decentralization of cities throughout the UnitedStates，( )when massive highway-building programs permitted greater suburban growth.

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单选题

Hawass said the collection of workers’ tombs, some of ______ were found in the 1990s, were among the most significant findings in the 20th and 21st centuries.

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单选题

Equipment without significant effect on the weight or balance of the airplane need not be listed.

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