And every atom except the sea atom, except our carbon can form two more additional bonds with lowest bases. Now remember what a lewis bases. It's simply an atom or a molecule that has an extra lone pair of electrons that it can donate to some other lewis acid. Now let's look at D. Now, only carbon is capable of forming strong pi bonds. In other words, it can form a strong double bond or a strong triple bond. No other atom found in our group 14 or four A has that capability.