What Was the Main Impact of the Introduction of Metal

What was the main impact of the introduction of metal to ancient India by the Aryans?

A) production of more powerful weapons that defeated their adversaries.
B) the conquering of the southern half of India, as well as the northern part.
C) the ability to cultivate new and better crops.
D) a return to their former nomadic lifestyles.
E) tying the use of the horse and the plow to cultivation.