单项选择题

It may be inferred from the passage that jets of gas ______.

A．around Sagittarius A were found quite unexpectedly
B．are common phenomena surrounding enormous black holes
C．only flow away from the centers of galaxies
D．are the true source of intense energy

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单项选择题According to the passage, which of the following is TRUE

A．Energy only emits from Sagittarius A.
B．There are many strong energy sources.
C．Energy comes from a black hole.
D．Energy emits from any regions surrounding Sagittarius A.

单项选择题According to the German researchers, the energy source at the center of the Milky Way Galaxy ______.

A．has been covered up by vast clouds of dust and gas
B．still remains unknown to astronomers
C．has proved to be a black hole
D．actually provides power for the rotation of file great spiral of stars