1. 凸面   straight line   vertex   plane   convex   Hint Half-n-half Clue   2. 直線   straight line   quadrangle   hemisphere   oval   Half-n-half Clue   3. 長円   ellipse   parallelogram   convex   ray   Half-n-half Clue   4. 多角形   quadrilateral   parallelogram   heptagon   polygon   Half-n-half Clue   5. 頭頂　   straight line   heptagon   plane   vertex   Half-n-half Clue   6. 四角形   heptagon   quadrangle   polygon   perpendicular lines   Half-n-half Clue   7. 菱形, 斜方形　   plane   rhombus   ellipse   hemisphere   Half-n-half Clue