Sentence Correction

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
C. with large, integrated companies, such as Bethlehem Steel, that
D. while large, integrated companies, such as Bethlehem Steel, that
E. and large, integrated companies such as Bethlehem Steel

pls explain your answer