Which of the following samples of gas, when sealed into a vessel of volume 0.10m³, is at the highest pressure?

a) 1 mol of nitrogen (Nâ‚‚)
b) 2 mol of oxygen (Oâ‚‚)
c) 0.5 mol of helium (He)
d) 3 mol of carbon dioxide (COâ‚‚)