The correct option is A Allotropy
The property by which elements exist in different states is called allotropy. The allotropes of carbon exist in two forms -amorphous and crystalline.
Graphite, diamond and fullerene are examples of crystalline allotropes of carbon while coal, charcoal, etc are amorphous allotropes of carbon.
Tetravalency is the property by which an element can bond with four other atoms.
Catenation is the self linking property exhibited by an element by which it forms long chain or branched compounds. Elements like carbon, silicon, etc show catenation.