Is a diamond a homogeneous or heterogeneous mixture or a substance

heterogeneous

Explanation:

It's a heterogeneous mixture. Diamond is made of just one element: carbon. Each carbon atom in diamond is connected to four other carbon atoms, in a crystal that extends on and on. There are other forms of pure carbon where the atoms are bonded differently, notably charcoal and graphite.

the answer would be b i believe

with this one i know the answer in craters one reason i looked it up and i learned about it there is my evidence