subway line 4,put into use in september 2009,has made traveling in biejing
问题描述：
subway line 4,put into use in september 2009,has made traveling in biejing
subway line 4,(put) into use in september 2009,has made traveling in beijing easier.
a.having been put怎么错了
答
看时态.
4号线2009年投入使用.所以应该是一般过去式,没有必要用现在完成时的.