求助一道高中英语选择题!谢谢!______into use in April 2000,the hotline was
求助一道高中英语选择题!谢谢! ______into use in April 2000,the hotline was meant for residents reporting water and heating supply breakdowns. A.Put B.Putting C.Having put D.Being put 请说明一下为什么,谢谢!另外翻译一下句子!