问题
单项选择题
As it is used in the passage, the word "photosphere'' (Line 2, 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
答案
参考答案：B
解析：语义题。文中关于“photosphere”的说明只在第二段后半部分见到：作者指出，太阳从外到内分别是corona(日冕)，chromospheres(色环层)，和photosphere，然后作者又指出“The first three zones are regarded as the Sun's atmosphere．”photosphere也是太阳大气层中的一层，所以它应该是一种气体。A说它是一种“气体状包层”，不够准确。C内容与本文无关，错误。D选项将 photosphere和chromospheres的位置搞反了，也错。