The correct answer is B) ms⁻². Acceleration is the rate of change of velocity with respect to time. The S.I. unit for velocity is meters per second (m/s or ms⁻¹) and the S.I. unit for time is seconds (s). The unit of acceleration is derived by dividing the unit of velocity by the unit of time: (m/s) / s = m/s² = ms⁻². Options A, C, and D represent units of velocity (ms⁻¹), acceleration in CGS units (cms⁻²), and acceleration in a non-standard or larger unit (kms⁻²), respectively.