请帮忙讲解几道英语被动语态的习题
Great changes___ in the past ten years in China.
A.took place B.have taken place C.were taking place D.had taken place
You can't use the computer,it____.
A.was broken down B.is wrong C.is bad D.has broken down
Lookout,please keep away from the fire,or your trousers will__
A.burnt B.burn C.burning D.get burn