1) You mustn't read in bed.2) You shouldn't open the window. It is cold outside.3) It is already late. She mustn't go outside. He shouldn't dress so formal if he goes to a picnic.4) You mustn't keep books at home so long. 5) Parents mustn't obey their children.
1. Amy is buying souvenirs- she is visiting their friends in London .
2. William is studying the map of London -he is having a walk in the centre of London on their first day there .
3. Melanie and Amy are buying Carribean folk costumes.- They are taking part in the Notting Hill Carnival .
4.William is learning the British driving rules.- He is driving the car on the way from London to Edinburgh
4. It sounds like a frog.
It sounds like a monkey.
It sounds like a waterfall.
They sound like bees.
They sound like birds
Как правило речь идёт о письменной речи.Формальный стиль письма -деловой,отсутствуют сокращения.Неформальный-Личный,допускаются сокращения.
В устной речи можем отнести сленг к неформальному стилю общения.Неформальным стилем пользуются знакомые люди,друзья,в то время как формальный -научные статьи,отзывы на книгу,к примеру,речь президента,резюме,жалобы и т.д.