Answer:
D) it is the most common vehicle construction material.
A) it is a ferrous metal is true, Steel is a ferrous metal, which means it contains iron.
B) heat tends to strengthen high strength steel is true, heat treatment is often used to strengthen high strength steel.
C) Boron alloyed steel is exceptionally hard is also true, Boron alloyed steel is known for its exceptional hardness.
D) it is the most common vehicle construction material is False. Aluminium is also widely used in vehicle construction, especially in recent years because of its weight-saving properties.