在真空中的静电场中，作一封闭的曲面，则下列结论中正确的是（ ）.
A. 通过封闭曲面的电通量仅是面内电荷提供的
B. 封闭曲面上各点的场强是面内电荷激发的
C. 由高斯定理求得的场强仅由面内电荷所激发的
D. 由高斯定理求得的场强是空间所有电荷共同激发的
一点电荷q位于一立方体的中心，通过该立方体每个面的电通量为（）。
A. q/(ε0 )
B. q/(3ε0 )
C. q/(6ε0 )
D. q/(8ε0 )
What does the passage mainly tell us?
A. How to live with your roommates.
B. How to win the respect of your roommates.
C. How to be good friends with your roommates.
D. How to be nice to your roommates.
What’s the only way you will be able to live with your roommates according to the passage?
A. To have talks with your roommates often.
B. To be considerate towards your roommates.
C. To make compromises when problems arise.
D. To change your habits and ask your roommates to change theirs.
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