The writer regards the change to a "Plastic and Light Metal Age" in the near future as _________.

A．growth of cities and shrinking of suburban areas
B．growth of both rural and suburban areas
C．growth of urban and suburban areas
D．growth of suburban areas and shrinking of cities

A．there was a scarcity of wood and other building materials
B．bronze was less expensive than stone
C．stone was no longer available
D．more bronze than stone came into use