Ideal gas equation

I have this multiple choice question for homework. I used the ideal gas equation to work out the number of moles that were in each answer but I did not get the right answer.
The correct answer and how to do to it would be appreciated.

Which of these samples of gas contains the largest number of molecules? The gas constant R = 8.31 J K^-1 mol^-1.
A 5.0_X10^-4 m³ at 1.0_x10⁶ Pa and 300 K
B 4.0_X10^-3 m³ at 2.0_x10⁵ Pa and 400 KC 3.0_X10¹ m³ at 3.0_x10⁴ Pa and 500 KD 2.0_X10² m³ at 4.0_x10³ Pa and 600 K

Thanks in advance.

Which version of the ideal gas equation did you use and what exactly have you done?

I rearranged PV=nRT to n=PV/RT. Then I worked out the moles for each answer. I found that C had the largest number but it was wrong.