Rewrite:
1, Lan is more stupid than Linh. (Linh) 2, Nam is the naughtiest noy in class. (No boy)
3, A year has four seasons in Vietnam. (There) 4, Her hobby is to look after her cat in her free time. (She)
5, She is a graceful woman.(How) 6, Working in a medical factory is very dangerous for human beings.(It's)