A. Food chain
A food web also shows the flow of energy and materials through an ecosystem but in a complex web, not a single chain. A biogeochemical cycle does not deal with the flow of energy/materials through an ecosystem at all.
Answer:
The force exerted on an electron is 
Explanation:
Given that,
Charge = 3 μC
Radius a=1 m
Distance = 5 m
We need to calculate the electric field at any point on the axis of a charged ring
Using formula of electric field


Put the value into the formula


Using formula of electric field again

Put the value into the formula


We need to calculate the resultant electric field
Using formula of electric field

Put the value into the formula


We need to calculate the force exerted on an electron
Using formula of electric field


Put the value into the formula


Hence, The force exerted on an electron is 
Answer: There are number of electrons.
Explanation:
We are given 50 Coulombs of charge and we need to find the number of electrons that can hold this much amount of charge. So, to calculate that we will use the equation:
where,
n = number of electrons
Charge of one electron =
Q = Total charge = 50 C.
Putting values in above equation, we get:
Hence, there are number of electrons.
Answer:
the speed of light in air is about 299,000,000 and 3×10⁸ m/s