If several musicians were to play the same melody in unison, the texture would be

The texture would be heterophony, if the musicians have used the same melody in unison. This type of texture has a line of which it only has a single melody with its simultaneous variations. This type of texture could be incorporated with two or more performers.

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).