98% of human body is made up of six elements that is Carbon, Hydrogen, Nitrogen, Oxygen, Calcium and Phosphorous. Out of which, Carbon is the main element present in the human body because it is the main unit of all organic compounds. Secondly, Calcium is the main component present in bones and also, the most abundant mineral present in the human body. Lastly, phosphorous is present in ATP molecules and a little in bones too. Hence, the correct option is (d) which is sodium.