Which element is structural part of haemoglobin of our blood ?

The correct answer is (c) Iron.

Haemoglobin is a protein found in red blood cells that carries oxygen from the lungs to the rest of the body. It is made up of four subunits, each of which contains a heme group. The heme group is a complex of iron and protoporphyrin IX, and it is this iron atom that binds to oxygen.

Copper is an essential mineral for human health, but it is not a structural part of haemoglobin. Calcium is also an essential mineral, but it is not involved in the transport of oxygen.

Therefore, the correct answer is (c) Iron.