The ferrous metals are mainly made from （）

A. iron
B. copper
C. alluminium
D. alloy

The metal used in concrete is called （）

A. wrought steel
B. structural steel
C. reinforcement
D. hot-rolled steel

The corrosion resistance of steel may be enhenced in 3 ways, not including （）

A. protective coatings of paints
B. thermally treated
C. cathodic protection
D. alloyed steel

The properties of metals which make them unique among constructional materials arethe（）、（）、（）

Metal consist of （）and （）

Plain carbon steel has good ductility and weldabllity if its carbon contest is （） and a high yield strength if its carbon content is（）.