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.

1. as large, integrated companies such as Bethlehem Steel
2. as large, integrated companies, such as Bethlehem Steel, that
3. with large, integrated companies, such as Bethlehem Steel, that
4. while large, integrated companies, such as Bethlehem Steel, that
5. and large, integrated companies such as Bethlehem Steel

答案是B，我选E

as large, integrated companies, such as Bethlehem Steel, that  

这个逗号为什么加? 如果没有这个逗号 应该是正确的。