I'm not entirely sure but I would think it's A.
Answer:

Explanation:
Given:
Force between pair of charges= 900 newtons
The distance between the charges = 0.01 meters
Strength of Charge first q1 = 2e-10 Coulomb
To find:
Strength of Charge second q2 = ____ Coulomb?
Solution:
We know that,
Force between two charges separate by distance r is given by the equation,


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The answer that you are looking for is D.
Answer: Chromosphere hope this helps :)
The two largest natural cycles where convection currents occur are :
the movement of air in the atmosphere and
the movement of magma in the earth's mantle.