1. 平行的线   parallel lines   rhombus   parallelogram   heptagon   Hint Half-n-half Clue   2. 凸面   convex   straight line   prism   oval   Half-n-half Clue   3. 四边形   hexagon   polygon   segment   quadrangle   Half-n-half Clue   4. 边缘   ellipse   plane   edge   quadrilateral   Half-n-half Clue   5. 平行四边形   parallelogram   hexagon   edge   pentagon   Half-n-half Clue   6. 七边形   parallelogram   pyramid   prism   heptagon   Half-n-half Clue   7. 卵形   prism   ellipse   oval   concave   Half-n-half Clue