Question

Which of the folllowing is the a unit force? And why? A) kilogram B) newton c) kg-m/sec D) m/sec2

Answer 1

F = ma, yes?

So what ever the units of force, F, are, they had better match the units of mass, m, times the unites of acceleration, a.

Now the units of mass, m, are kilograms: kg.
The unites of acceleration, a, is meters per second squared: m/s^2

Hence the units of force must be

kg. m/s^2

Is that on the list? No.

Force is such an important concept, that this unit is given a special name all to itself.

1 kg.m/s^2 is called 1 Newton.

The abbreviation for Newton is N.

You have your answer.