Bats are the only mammal capable of flying and are so highly evolved to be capable of pinpointing a single insect flying in the pitch black and plucking it out of the air using echo location.

蝙蝠是唯一会飞的哺乳动物，进化程度很高，能够在一片漆黑中精确定位一只飞虫的位置，并利用回波定位准确地从空中捕捉。

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Since x-rays travel at the speed of light, the echo indicates that an object fell into the black hole around 350 years ago.

因为X射线以光速运行，因此反射表明，大约在350光年前，有一个物质落入黑洞。

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At that time, I have forgotten what is not said, but it is certainly echo the black joke everyone said, laughing off or expressed support.

我已忘记了当时有没有说过甚么话，但肯定是附和了大伙说的黑色笑话，笑过或表示过认同。

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Black churchgoers, of course, often do the same thing at Sunday-morning services, and I suspect that the amenlike responses of black theatergoers are a not-so-distant echo of that old-time religion.

WSJ: Theatergoers: Can I Get an Amen? | Sightings by Terry Teachout