Find the odd pair out.

In the given option constituent of an element is given. Air is composed of nitrogen and oxygen . Match stick is made up of phosphorous and sulphar. Water is made up of hydrogen and oxygen. Stainless steel is a metal alloy, made up of steel mixed with elements such as chromium, nickel, molybdenum, silicon, aluminum, and carbon. Iron mixed with carbon to produce steel is the main component of stainless steel.Chromium is added to make it resistant to rust.