1) I'm the happiest boy in the world.
2) That is the slowest car in the world.
3) That is the best bike in the shop.
4) That is the biggest bag I have.
5) That is the funniest song in the book.
6) Russia is the largest country in the world.
7) David is the shortest boy in our class.
8) That is the most beautiful doll I have.
9) That is the most interesting text in the lesson.
10) That was the worst holiday.