Explain how red blood cells are adapted to carry out their function?

Red blood cells transport oxygen from the lungs to all the cells in the body. To do so effectively, they have lots of adaptations: Red blood cells contain haemoglobin, which is a molecule that reversibly binds to oxygen. Red blood cells have no nucleus, so that there is more room for haemoglobin in the cell. Red blood cells have a biconcave disc-like shape (it is thinner in the middle than at the edge) which increases the surface area. Red blood cells are very flexible which means they can pass through the narrow capillaries easily.Key word is explain, so must ensure that there is a link between identifying a feature/adaptation of a red blood cell and how this feature allows them to perform a specific function more effectively.