these trials, people are ________assigned to a "treatment" group, which benefits from the project, and a "control" group, which does not.

A. initially B. conventionally

C. superbly D. randomly

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Time Travel

If you could travel in time, where would you go? Perhaps you would watch an originalperformance of a Shakespeare’s play in Elizabethan England?

What about hanging out with Laozi in the Spring and Autumn Period? Or maybe you’d voyage far ahead of the present day to see what the future holds.

The possibility of time travel is indeed appealing. Stories exploring the subject have been around for hundreds of years. Perhaps the best known example is science fiction novel The Time Machine, which was written by H.G.Wells and published in 1895 for the first time. It was adapted into at least two feature films of the same name, as well as two television versions, and a large number of comic book adaptations. It is generally credited with the popularization of the concept of time travel using a vehicle that allows an operator to travel purposefully and selectively. The term “time machine”, coined by

Wells, is now universally used to refer to a vehicle transporting people into the far future.

But could time travel actually be possible? Some scientists say yes, in theroy. They propose using cracks in time and space called“wormholes”,which could be used as shortcuts to other periods．Einstein's theory of relativity allows time travel in extreme circumstances．And British physicist Stephen Hawking says you could travel into the future with a really fast spaceship—going at nearly the speed of light．Though building such a spaceship would of course be no simple task．

Even if you could travel into the past, there is something called the “grandfather paradox”．It asks what would happen if a time traveler were to go back in time and have his own grandfather killed for some reason, and therefore prevent himself from being born．If the time traveler wasn't born, how would he travel back in time？

And would you really like to visit the future？In H．G．Wells' book,the main character travels into distant time where he arrives at a beach and is attacked by giant crabs．He then voyages 30 million years into the future where the only living thing is a black object with tentacles（觸角）.

If that's what's in store, maybe we are better just living in the present day after all．

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B．the special feature of the book

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D．the contribution of H．G．Wells

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C．Supportive．D．Unconcerned．

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