）中国无疑已经在国际事务中起到了越来越重要的作用.（play a role）医生们总是告诫我们说维生素药片不能取代均衡膳

Doutelessly,China has played a more and more important role in the international affairs。Doctors always warn us that the Vitamin pills cannot substitute balanced diet。Until now,people in many areas has not yet recognized the danger of air pollution。He went to the bookstore and picked up many books at bargain prices。The fireman who ran into the burning house to rescue the twin sisters sacrificed。