Which best defines partial pressure in a mixture of gases

Partial pressure is the pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own. For a mixture of gases, each gas has a partial pressure which is the hypothetical pressure of that gas if it alone occupied the volume of the mixture at the same temperature.

The answer to this one is c

A) the enthralling of formation for pure element in its standard state is always positivehope this : )