Writing. 1 The Mekong river is longer than the Red river .The Red river is ..................................... 2 Banana is cool , Dalat is cooler and Sapa is the coolest. Sapa is .......................................... 3 It is wrong of you to talk in class.You mustn't ....................... 4 I'm the tallest in the class. Nobody is .................................... 5 It is necessary for us to finish homework before going to class.We must ..............................................