Coulombs law says that the force between any two charges depends on the amount of charges and distance between them. This force is directly proportional to the magnitude of the two charges and inversely proportional to the distance between them.

where
are charges,
is the distance between them and k is the coulomb constant.
case 1:

case 2

case 3:

Comparing the 3 cases:
The maximum potential force according to coulombs law is between -1 charge and +3 charge separated by a distance of 100 pm.
Answer:
according to this question best answer is C
The height to which the weight-watcher must climb to work off the equivalent 991 (food) Calories is 0.59 Km
<h3>How to determine the energy. </h3>
1 food calorie = 103 calories
Therefore,
991 food calories = 991 × 103
991 food calories = 102073 calories
Multiply by 4.2 to express in joule (J)
991 food calories = 102073 × 4.2
991 food calories = 428706.6 J
<h3>How to determine the height </h3>
- Energy (E) = 428706.6 J
- Mass (m) = 73.9 kg
- Acceleration due to gravity (g) = 9.8 m/s²
E = mgh
Divide both side by mg
h = E / mg
h = 428706.6 / (73.9 × 9.8)
h = 591.95 m
Divide by 1000 to express in km
h = 591.95 / 1000
h = 0.59 Km
Learn more about energy:
brainly.com/question/10703928
let us consider that the two charges are of opposite nature .hence they will constitute a dipole .the separation distance is given as d and magnitude of each charges is q.
the mathematical formula for potential is 
for positive charges the potential is positive and is negative for negative charges.
the formula for electric field is given as-
for positive charges,the line filed is away from it and for negative charges the filed is towards it.
we know that on equitorial line the potential is zero.hence all the points situated on the line passing through centre of the dipole and perpendicular to the dipole length is zero.
here the net electric field due to the dipole can not be zero between the two charges,but we can find the points situated on the axial line but outside of charges where the electric field is zero.
now let the two charges of same nature.let these are positively charged.
here we can not find a point between two charges and on the line joining two charges where the potential is zero.
but at the mid point of the line joining two charges the filed is zero.