Batteries always use direct current. That eliminates A and C. The other part of the answers is just asking what direct/alternating means. Alternating currents change directions moving one way then another. Direct current only moves in one direction. Therefore, the answer is D, since the current is direct and direct currents move in one direction.
To solve this problem we will apply the concepts related to the Electrostatic Force given by Coulomb's law. This force can be mathematically described as
Here
k = Coulomb's Constant
Charge of each object
d = Distance
Our values are given as,
d = 1 m
a) The electric force on charge 
is
Force is positive i.e. repulsive
b) As the force exerted on will be equal to that act on 
,
Force is positive i.e. repulsive
c) If 
, a negative sign will be introduced into the expression above i.e.
Force is negative i.e. attractive
Answer: Hot spot
The volcanic hot spot is an area in the mantle from which heat rises as a thermal plume from deep in the Earth.
Answer:
I think is Number 2
The rate at which calcium chloride is equal to the rate at which sodium chloride is produced.
Let me know if I'm wrong.
Answer: false.
Explanation:
Doppler effect is caused to the relative motion of the source of light/sound with respect to the observer.
If the source is moving towards you, you will perceive the frequency to be larger (also called a blue shift), while if the wave is moving away, you will perceive the frequency to be smaller (also called a red shift).
Then the statement:
"Doppler effect is caused by sound or light wave being pushed together and spread apart due to motion."
Is false
