a and b are dimensionally homogenous but c and d aren't.
Force = N (newtons) = kg * m/s^2
Therefore,
a) F = m* a = kg m/s^2 (since m (mass) = kg and a (acceleration)= m/s^2) = kg m/s^2
b) F = m*(v^(2)/r)= kg * ((m/s)^(2)/m) = kg m/s^2 = kg m/s^2
c) F = m * (v2-v1)= kg * (m/s - m/s) = kg m/s ≠ kg m/s^2
d) F= m * v = kg * m/s ≠ kg m/s^2
Hope this helps