1. 凹面   pyramid   prism   parallelogram   concave   Hint Half-n-half Clue   2. 段   heptagon   oval   vertex   segment   Half-n-half Clue   3. 半球   concave   straight line   hemisphere   pyramid   Half-n-half Clue   4. 凸面   rhombus   concave   hemisphere   convex   Half-n-half Clue   5. 垂直線   perpendicular lines   pentagon   polygon   rhombus   Half-n-half Clue   6. 平行的線   plane   segment   vertex   parallel lines   Half-n-half Clue   7. 平行四邊形   hemisphere   parallel lines   parallelogram   oval   Half-n-half Clue