2.Cats are(nice) that lizards(ответ): nicer
3.Dolphins are (clever) than whales(ответ): cleverer
4.Giraffes are (thit) than hippos(ответ): thinner (думаю,что там опечатка и нужно thin)
5.I"ts (hot) in summer than in autumn(ответ): hotter
6.Lena is (pretty) than Tamara(ответ): prettier
7.Gena is (friendly) that Arytyom (ответ): friendlier