单项选择题

A．Sagittarius A is a powerful emitter of radio wavesB．a……

Were it not for the new telescope high in the Andes Mountains, researchers would not have argued that ______.

A．Sagittarius A is a powerful emitter of radio waves
B．a super-massive black hole contains as much as a million suns
C．Sagittarius A is a super-massive black hole
D．Sagittarius A lies just at the center of the Milky Way Galaxy

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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

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