The writer of the passage makes the point that the major part of the iron and steel industry of Germany ----.

The Rhine - Ruhr area became the greatest industrial
region of Germany, because it had at its heart the
great coal field of the Ruhr. Mining is now almost
entirely northeast and westwards across the Rhine.
The region contains the greater part of the German
iron, steel and heavy engineering industries. The
great integrated iron and steel plants mostly cluster
on the Rhine waterway. Specialized steel plants and
engineering works are more widespread. With a
decline in coalmining and the dismantling after World
War II of certain steel plants, some of the older Ruhr
towns have diversified their industries considerably:
vehicles, electrical goods and clothing are now being
produced.