At a particular temperature and pressure, 1 mol of gas M occupies 45 liters. ... ...

At a particular temperature and pressure, 1 mol of gas M occupies 45 liters. If the density of gas M at the same temperature and pressure is 1.8 g/L, the molecular weight of gas M is:  
(A) 25 g/mol.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in 06. Gases