Air resistance doesn't appear in the formula for gravitational force, because it doesn't affect it. Mass does because it does.
Answer:
gravitational force
electrostatic force
Explanation:
The forces that balloons may exert on each other can be gravitational pull due to the mass of the balloon membrane and the mass of the gas contained in each. This force is inversely proportional to the square of the radial distance between their center of masses.
The Mutual force of gravitational pull that they exert on each other can be given as:

where:
gravitational constant 
are the masses of individual balloons
the radial distance between the center of masses of the balloons.
But when there are charges on the balloons, the electrostatic force comes into act which is governed by Coulomb's law.
Given as:

where:

are the charges on the individual balloons
R = radial distance between the charges.
Answer:
B. Its density is lower than that of water
Explanation:
density = mass / volume
density of the liquid = 85 / 100 = 0.85 g/cm^3
now,
density of water is 1 g/cm^3 which is greater than the density of the given liquid ( 0.85 g/cm^3 )