What secondary color would fill in the circle for number2

A color produced by mixing two additive primary colors in equal proportions.

Explanation:

A color produced by mixing two additive primary colors in equal proportions.

option c (nickel) is not found in earth's crust. the earth's crust basically contains eight (8) elements namely: oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium (listed in order of abundance).