ANS:C - 9.81 kg mass

One metric slug is equal to 9.81 kg mass. The slug is a unit of mass in the British gravitational system and is defined as the mass that is accelerated at a rate of 1 foot per second squared (1 ft/s²) when a force of one pound-force (lbf) is applied. In the metric system, the equivalent of a slug is the kilogram (kg), and the conversion factor is 1 slug = 9.81 kg mass. Therefore, one metric slug is equal to 9.81 kg mass.