按要求完成句子。

1．They're staying for two weeks.（对画线部分提问）

    _________ ________are they staying?

2．I forgot my pen when I left my room.（改为同义句）

  I_____________ my pen in my room.

3．She's going fishing for vacation.（对画线部分提问）

   _________ is she doing for vacation?

4.They go for a walk after supper every day.（改为同义句）

  They________ _________after supper every day.

外层钢丝绳磨损达到其直径的（）应报废。

A、30%

B、25%

C、40%

D、20%