Answer:
The correct answer is 5s
Explanation:
Strontium atomic number = 38
Electronic configuration is 
As
orbital is valence orbital in strontium, the outer electrons exists in that orbital only.
Hydropower is one of the oldest renewable resources and has been used for thousands of years.
Answer: 
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
The balanced equation will be:

O they did not
at least thats what my substitute teacher said