The correct option is
A carbon
Let us consider one configuration 2, 4.
Here it can either accept or share four electrons hence tetravalent.
Carbon atoms are very small, and therefore form very strong bonds, particularly with themselves.
Carbon has the ability to 'catenate', forming long chains of carbon-carbon bonds, which theoretically can have an infinite number of carbons in them.
The diversity of organic compounds is due to this ability. Carbon may form single bonds, double bonds, even triple bonds and it can bond with many other elements like nitrogen, oxygen, halogens and of course hydrogen.
Hence the correct option is A.