1. 凸面   perpendicular lines   edge   convex   heptagon   Hint Half-n-half Clue   2. 卵形   parallel lines   vertex   polygon   oval   Half-n-half Clue   3. 直线   straight line   parallel lines   quadrilateral   convex   Half-n-half Clue   4. 端点   vertex   perpendicular lines   polygon   oval   Half-n-half Clue   5. 半球   ellipse   hexagon   quadrangle   hemisphere   Half-n-half Clue   6. 凹面   concave   pyramid   ellipse   pentagon   Half-n-half Clue   7. 金字塔   straight line   segment   convex   pyramid   Half-n-half Clue