the ideal gas constant, r has several different values that could be used. which quantity causes these…

Brief Explanations:

The value of the ideal - gas constant $R$ depends on the units of pressure, volume, temperature, and amount of gas. Different combinations of units for these quantities lead to different values of $R$. For example, if pressure is in atmospheres, volume in liters, temperature in Kelvin and amount in moles, $R = 0.0821\ L\cdot atm/(mol\cdot K)$. If pressure is in Pascals, volume in cubic meters, temperature in Kelvin and amount in moles, $R= 8.314\ J/(mol\cdot K)$. So the differences in the value of $R$ are due to the units of pressure, volume, temperature and moles. Among the given options, pressure is the key factor as changing the unit of pressure (e.g., from atm to Pa) while keeping other units consistent can change the value of $R$.

Answer:

pressure