Fractional distillation is used to separate gases from liquid air. The boiling points of four gases are given below. Which gas is monoatomic and also a liquid at $-200\,^{\circ}\text{C}$?
- Aargon ($-186\,^{\circ}\text{C}$)
- Bhelium ($-269\,^{\circ}\text{C}$)
- Cneon ($-246\,^{\circ}\text{C}$)
- Dnitrogen ($-196\,^{\circ}\text{C}$)