The world’s elderly population will exceed(超过) ____ of children by 2060, when each group ____ to account for about one fifth of the population.

Low-carbon lifestyle is of great benefit to improve the world environment. _______ can be enjoyed from it until you have a deep under, standing of it, however.

---Doris, do you have anything in mind______________ you’d like for breakfast ?
---_______________ is okay with me. I’m not particular about food.

—Can I have ________ apple?
—Oh, your sister has just had it.

She brought with her three friends, none of _____ I had ever met before.

He had lost his temper and his health in the war and never found ____ of them again.

--Have you got a digital camera?
---No.
---You should buy________.

---Mum, have you seen my U-Disk?
---____________ you bought last Sunday? I'm afraid I haven't seen ________.

If our parents do everything for us children, we won't learn to depend on                   
       .

Make sure you’ve got the passports and tickets and _______ before you leave.