1.Scientists have done a lot of _____________(研究)on H1N1 flu.
2.He has to wear a shirt and _____________(领带)for the party tonight.
3.Lisa’s job and family are great _____________(烦恼)to her parents.
4.Could you please _____________(介绍)your pen-pal to us?
5.We all think Jenny is a good _____________ (listen).
6._____________ (million) of young people want to be volunteers for the Olympic Games.
7.People cut down plenty of _____________ (tree) every year.
8.You can’t use your dad’s car without his _____________ (permit).