1. 椭圆   ellipse   parallelogram   vertex   edge   Hint Half-n-half Clue   2. 段   rhombus   perpendicular lines   segment   pyramid   Half-n-half Clue   3. 光芒   vertex   ray   parallelogram   hemisphere   Half-n-half Clue   4. 菱形   ellipse   straight line   rhombus   perpendicular lines   Half-n-half Clue   5. 飞机   plane   rhombus   concave   oval   Half-n-half Clue   6. 多角形   parallel lines   polygon   pyramid   plane   Half-n-half Clue   7. 凹面   concave   perpendicular lines   parallelogram   hemisphere   Half-n-half Clue