Answer
D- Carbon
Step-by-step explanation:
Carbon, as an element, is the basis of what is referred to as diamond, graphite, and coal. Coal is a solid form with high content of hydrocarbon making coal amenable to burning). In a much purer form Carbon occurs in graphite and diamond. While in graphite carbon atoms bond to two neighboring atoms, in diamond they do so to four neighboring carbon atoms in a "tetrahedron-like" configuration (making diamond very hard).