The correct option is C Cl
Symbols of most of the elements are taken from the first letter of the element's names in English.
Elements like carbon, chromium, cobalt, etc. also have "C" are their first letter.
If the first two letters of the elements are the same, then use the next prominent letter for writing the symbol. For chlorine, "l" is the next prominent letter, so "Cl" is the chemical symbol.