The correct answer is the last one:
A and C are different elements, while D is an isotope of C.
In fact, A and C are different elements, because they have a different number of protons in the nucleus (A has 3 protons, while C has 4 protons). Instead, D and C are the same element (they both have 4 protons in the nucleus), but they are different isotopes since they have a different number of neutrons (D has 4 neutrons while C has 3 neutrons)
One cubic centimeter and one milliliter are equal volumes.
A table would be the most appropriate because that way you can compare the data.
To solve this problem we need to use the proportional relationships between density, mass and volume, together with Newton's second law.
The force can be described as

Where,
m = Mass
g = Gravitational acceleration
At the same time the Density can be defined as

Where,
m = mass
V = Volume
Replacing the value of the mass at the equation of Force we have,

Since the difference between the two forces gives us the total Force then we have to

Where
Force of the water
= Force of plastic
Therefore with the values for this force we have,





Therefore the tension in the thread is 16.412N