The density of an ideal gas

Value of absolute zero of temperature in degree Celsius (.^(@)C) can be determined by given data. The density of an ideal gas at 25^(@)C and 100^(@)C are 1.5 and 1.2g/L, respectively, both at the same pressure. The value of absolute zero of temperature in degree Celsius (.^(@)C) :

Relation between density of an ideal gas and its molar mass is given as_______

The density of the ideal gas is given by

If the pressure, temperature and density of an ideal gas are denoted by P.T and rho respectively. The velocity of sound in the gas is

Which of the following shows the correct relationship between the perssure and density of an ideal gas constant temperature ?