1. =>You must return this book to the library within five days => This book must be returned to the library within five days

2. =>“Please don’t talk in class”. Lan told us. => Lan told us not to talk in claass

3.=> The house was cheap so we decided to buy it.=>Because the house was cheap, we decided to buy it.

4.=> The news was so good that she smiled all the time.=>  It was such good news that she smiled happily.

5. =>We can’t go swimming because of bad weather.=>The weather is too bad to go swimming