The correct option is A Iron
Deficiency of any essential elements may lead to externally visible morphological changes called deficiency symptoms. Chlorosis is one of the deficiency symptoms. It is non-development or loss of chlorophyll. It leads to the yellow colour of leaves. It is caused by deficiency of iron. Iron is one of the essential micronutrients. It is essential for the formation of chlorophyll and other pigments. So, its deficiency leads to loss of chlorophyll.