The Symbol of Carbon :

Explanation:

The symbol for chromium is Cr.
We can get the symbol by taking the first and third letters of the word chromium.
Calcium is represented by the symbol Ca.
We can get the symbol by taking the first two letters of the word calcium.
Co is the cobalt symbol.
We can get the symbol by taking the first two letters of the word cobalt.
Carbon's correct symbol is C, and its atomic number is 6.

Final Answer:

Hence, the correct option is (a) i.e., C.