The standard unit for measuring pressure is typically considered to be the pascal (Pa), but if you are looking for options among those provided, the most commonly recognized standard unit related to atmospheric pressure is:
a. 1 atm
This represents standard atmospheric pressure. Other units like mmHg and torr are also used, with 1 atm being equal to 760 mmHg or 760 torr, and 1 atm being approximately equal to 101.325 kPa. However, in the context of standard atmospheric pressure, 1 atm is the most recognized.