We usemustn'twhen we want to saythat something is not allowed. e.g. You mustn't somoke here. READING FOR FUN The Polar Bear PBC = POLAR BEAR CUB (北极熊幼崽) PMB = POLAR BEAR MOTHER (北极熊妈妈) PBC: Mum, am I real polar bear? PBM: Yes,dear,of course you are. PBC: Really?