Solution

Magnesium is a constituent of chlorophyll. Chlorophyll are the green photosynthetic pigments. Five types of cholorophyll a, b, c, d and d and e occur in the chloroplasts of higher plants. Molecular formula of chlorophyll a, b ,c and d are $$C_{55} H_{72} O_{5} N_{4} Mg , $$ $$ C_{55} H_{70} O_{6} N_{4}Mg, $$ $$C_{35} H_{32} O_{5} N_{4} Mg$$ and $$C_{54} H_{70} O_{6} N_{4} Mg$$ respectively . Chlorophyll e is a rare type found in some golden algae.So, the correct answer is 'Magnesium'.