Option B is the correct answer.
MKS system gives the following units:
Distance ----- meters
Mass ----- Kilograms
Time ----- seconds
meter is basic unit for length measurement. smaller units are centimeter, millimeter, micrometer, bigger units are kilometer and so on.
kilogram is the basic unit for mass. smaller unit is gram.
second is the basic unit for time. Greater units are minutes, hours, smallest unit are micro second and so on.