求教一道语法题~GWD第22套第15题，编号是GWD4-Q17~

MMMangOOO

The steel industry has changed radically over the last two decades, 【as large, integrated companies such as Bethlehem Steel】 once conducted operations from mining at one end of the process to shipping at the other have greatly downsized, or in some cases shut down altogether.
A.as large, integrated companies such as Bethlehem Steel
B.as large, integrated companies, such as Bethlehem Steel, that

主要是A和B判断不出来，我理解的是：
钢铁业过去20年发生了巨大变化，（这样的变化是发生在）当大型公司<像B公司曾经将经营活动blahblahblah一样>的时候。
如果是这样的话，为毛such as B Steel还要加个that？
应该是我理解错了吧。。
但是应该怎样理解才能说得通B是正确答案呢？
小女子跪求大神赐教！

MMMangOOO

o o o理解了！谢谢咯~

superbat28

that跳跃插入语，修饰companies，这些companies曾经conducted operations from on side to the other side