Answer:
a

b

Explanation:
From the question we are told that
The mass of the rock is 
The length of the small object from the rock is 
The length of the small object from the branch 
An image representing this lever set-up is shown on the first uploaded image
Here the small object acts as a fulcrum
The force exerted by the weight of the rock is mathematically evaluated as

substituting values


So at equilibrium the sum of the moment about the fulcrum is mathematically represented as

Here
is very small so
and 
Hence

=> 
substituting values


The mechanical advantage is mathematically evaluated as

substituting values


The correct answer to the question is : B) The weight of the water, and C) The height of the water.
EXPLANATION :
Before coming into any conclusion, first we have to understand potential energy of a body.
The potential energy of a body due to its position from ground is known as gravitational potential energy.
The gravitational potential energy is calculated as -
Potential energy P.E = mgh
Here, m is the mass of the body, and g is the acceleration due to gravity.
h stands for the height of the body from the ground.
We know that weight of a body is equal to the product of mass with acceleration due to gravity.
Hence, weight W = mg
Hence, potential energy is written as P.E = weight × height.
Hence, potential energy depends on the weight and height of the water.
Answer:
Normal force, 
Explanation:
Let
is the weight of suitcase. A man attempts to pick up his suitcase by pulling straight up on the handle. The weight of the suitcase in downward direction. The normal force is acting in upward direction. Let F is the force with which it is pulled straight up.
So, the normal force is given by :

N = mg - F
mg is the weight of the suitcase.
Hence, this is the required solution.