Given that four pairs of force and mass.
(1) Force, F1 = 12 N and mass, m1 = 1 kg
(2) Force, F2 = 60 N and mass, m2 = 2 kg
(3) Force, F3 = 1 N and mass, m3 = 0.2 kg
(4) Force, F4 = 5 N and mass, m4 = 0.35 kg
To find the least acceleration among these.
In order to find the least acceleration, we have to find the acceleration of each pair.
According to Newton's second law,

Here, a is acceleration, F is force and m is the mass.
For the first pair,

For the second pair,

For the third pair,

For the fourth pair,

On Comparing all the values of acceleration, the third pair (force=1 N and mass m=0.2 kg ) has the least acceleration of 5 m/s^2.