单项选择题

The paragraphs following the passage most likely discuss which of the following

A．The remaining layers of the Sun.
B．The evolution of the Sun to its present form.
C．The eclipse of February 1979.
D．The scientists who study astronomy.

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单项选择题

As it is used in the passage, the word photosphere (Line 3, Para. 2) means______.

A．a scarlet gaseous envelope surrounding the Sun
B．the luminous envelope of gas surrounding the Sun
C．the mixture of gasses that surrounds any planet or star
D．the luminous irregular envelope of highly ionized gas outside the chromospheres of the Sun

单项选择题

With what topic is the second paragraph mainly concerned

A．How the Sun evolved.
B．The structure of the Sun.
C．Why scientists study the Sun.
D．The distance of the Sun from the planets.