A. 正常; B. 正常或升高; C. 正常或下降; D. 极度下降。
A. 椭圆 B. 直线 C. 点 D. 正多边形
A. the period of darkness exceeds the period of light B. there is only a partial eclipse of the light C. the periods of light and darkness are equal D. the period of light exceeds the period of darkne