Answer: Option D. -> It does not depend on any parameter
:
D

The value of Gravitational constant is a universal constant and does not depend on any factor. It remains constant anywhere in universe and its value is equal to $6.67\times {10}^{-11}N{m}^{2}k{g}^{-2}$.

Answer: Option B. -> $F_1=F_2$
:
B

Newton's third law of motion states that: For every action, there is an equal and opposite reaction. So, $F_1=F_2$. Both forces will remain the same as the value of $G$(Universal gravitational constant), the mass of the earth ($m_1$), the mass of the sun ($m_2$) and the distance between the two bodies$\left(r\right)$ do not change for both cases. However, the acceleration of the bodies will be inversely proportional to their masses.

Answer: Option C. -> $6.7\times {10}^{-11}N{m}^{2}k{g}^{-2}$
:
C

$G$ is universal gravitational constant. Its value remains constant everywhere in the universe and gravitational force between bodies $m$ and $M$ separated by distance $r$ is given by:
           $F=\frac{GMm}{r^2}$
$\Rightarrow G=\frac{F{r}^2}{Mm}$
$\therefore$ Units of G are $N{m}^{2}k{g}^{-2}$
The value of Gravitational constant is   $6.7\times {10}^{-11}N{m}^{2}k{g}^{-2}$.

Answer: Option C. -> Spring-balance
:
C
Spring balance or spring scale measures weight (force) by balancing the force due to gravity against the force of an extended spring.

Answer: Option D. -> 20 m
:
D
Brandon experienced a free fall from the top of the tower and, thus, was under the acceleration due to gravity (g). 
Distance travelled in 2 seconds is equal to the height of tower which can be found out by applying equation of motion.
From second equation of motion, we have,
$s=u\times t+\frac{1}{2}\times g{t}^2$
where s- height of tower, u- initial velocity, t-time taken and g- acceleration due to gravity.
Since he fell from rest, u = 0
$s=\frac{1}{2}\times g{t}^2=\frac{1}{2}\times 10\times 2^2=20m$
Therefore, height of tower is 20 m.

Answer: Option D. -> it supports increased water pressure at the depth
:
D
The pressure in the liquid increases with depth. Thus, as depth increases, more and more pressure is exerted by water on the wall of a dam. A thicker wall is required to withstand a greater pressure, therefore, the wall of the dam is made with the thickness increasing towards base.

Answer: Option B. -> $10N$
:
B

Given,
Length of each side of the cube, $l=10cm=0.1m$
Density of water, $\rho =1000kg{m}^{-3}$
Acceleration due to gravity, $g=10m{s}^{-2}$
Volume of the cube, $V=l^3=(0.1{)}^3=0.001m^3$
Archimedes' principle states that the buoyant force acting on an object is equal to the weight of the fluid displaced by it.
In the given case, volume of cube is equal to the volume of water displaced.
Mass of water displaced (m) = Density of water $\times$ Volume of water displaced
$\Rightarrow m=1000kg{m}^{-3}\times 0.001m^3$ 
          $=1kg$
   
Weight of water displaced, W = mg
 $\Rightarrow W=1\times 10$ =$10N$ 
Hence, the buoyant force is $10N$.

Answer: Option A. -> Density
:
A

Density is a measurement that compares the amount of matter an object has to its volume. An object with much matter in a certain volume has high density. An object with little matter in the same amount of volume has a low density. Density is found by dividing the mass of an object by its volume.