The radius of the cylinder is equal to half the diameter:

The volume of the cylinder is given by:

where h is the heigth of the cylinder. Converting into meters,

And the density of the material will be given by the ratio between the mass and the volume:

The correct answer is
C. The battery
The battery is a device that provides a potential difference in the circuit, and so an electromotive force (e.m.f.) which pushes the electrons in the circuit from the negative pole towards the positive pole of the battery, so they move through the circuit. Therefore, it provides electrical energy.
This is an example of the Newton`s Second Law:
F = m * a
a = F / m
F = 8 N, m = 2 kg.
a = 8 N : 2 kg
Answer:
a = 4 m/s²