Magnesium is the chief component of the chlorophyll. The magnesium ion is present in the +2-oxidation state in the Centre of the porphyrin ring in the chlorophyll molecule.
-If we chemically study the chemical structure of the chlorophyll, we come to know that the chemical formula of chlorophyll will be C55H72O5N4Mg.
Then we can easily see that magnesium is the element of chlorophyll.
Hence, option A is the correct answer.