D excretory system releases waste like when you use the bathroom and stuff. :)
Answer : The correct option is, (4) 6.0 mol
Explanation :
The given balanced chemical equation is,

In this reaction, lead undergoes reduction and chromium undergoes oxidation.
Oxidation reaction : It is the reaction in which a substance looses its electrons. In this oxidation state increases.
Reduction reaction : It is the reaction in which a substance gains electrons. In this oxidation state decreases.
Half reactions of oxidation-reduction are :
Oxidation : 
Reduction : 
From the reduction reaction, we conclude that 6 moles of electrons gained by the 3 moles of lead ions.
Hence, the correct option is, (4) 6.0 mole
Answer: Since all sodium atoms have 11 protons, this one has 11 protons. This tells us that it also has 11 electrons. Since the mass number is 23, we know that the sum of protons and neutrons in the nucleus must equal 23.
So the answer is : Mass number = 23
Explanation:
In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.