You can use Newton's Second Law which states:

Plug in given information:

This is closest to option
b which is your answer.
Answer:
The friction force acting on the object is 7.84 N
Explanation:
Given;
mass of object, m = 4 kg
coefficient of kinetic friction, μk = 0.2
The friction force acting on the object is calculated as;
F = μkN
F = μkmg
where;
F is the frictional force
m is the mass of the object
g is the acceleration due to gravity
F = 0.2 x 4 x 9.8
F = 7.84 N
Therefore, the friction force acting on the object is 7.84 N
Answer:
the less shielding of electrons
the answer is B 4-6 months thats when they can pick up large objects.