— Is Helen your sister? — Yes , ______.
--Why don’t you read this book? --It’s not necessary to read this book .There isn’tuseful in it .
--I don’t think teenagers should be allowed to smoke. --.
You should really _______ smoking. It’s a terrible habit.
Sixteen-year-olds shouldn’t ______ to go to an Internet bar.
The more careful you are, ________ mistakes you will make. I think it’s true.