1. 光芒   parallel lines   ray   plane   oval   Hint Half-n-half Clue   2. 端点   vertex   pentagon   prism   ray   Half-n-half Clue   3. 平行的线   concave   perpendicular lines   parallel lines   prism   Half-n-half Clue   4. 椭圆   parallelogram   concave   pyramid   ellipse   Half-n-half Clue   5. 四边形   hexagon   heptagon   ray   quadrangle   Half-n-half Clue   6. 飞机   rhombus   plane   heptagon   parallel lines   Half-n-half Clue   7. 凹面   straight line   edge   polygon   concave   Half-n-half Clue