My car has broken down .和My car is broken down.的区别

My car has broken down .和My car is broken down.的区别还有两题：8）He__to help the girl .Which one is WRONG?A.did all what he could .错误 应 把what改为that。WHY?(4)--what is the weather like here?---There ———— very little rain.A.has ; B.has been ; C.are ; have been PS;答案上说是选B。为什么