ANS:A - 1 mm Hg

1 torr is equivalent to 1 mm Hg (millimeter of mercury). Both torr and mm Hg are units of pressure commonly used in the field of fluid mechanics and particularly in the measurement of gas pressures. They represent the pressure exerted by a column of mercury (Hg) of 1 millimeter in height at standard gravity. Therefore, 1 torr is equivalent to 1 mm Hg.