?? Is that the whole question?
Answer:
B. control rods and moderators
Answer:
By absorbing energy electron is jump into higher energy level. This is called excitation.
Explanation:
The electron is jumped into higher level and back into lower level by absorbing and releasing the energy.
The process is called excitation and de-excitation.
Excitation:
When the energy is provided to the atom the electrons by absorbing the energy jump to the higher energy levels. This process is called excitation. The amount of energy absorbed by the electron is exactly equal to the energy difference of orbits. For example if electron jumped from K to L it must absorbed the energy which is equal the energy difference of these two level. The excited electron thus move back to lower energy level which is K by releasing the energy.
De-excitation:
When the excited electron fall back to the lower energy levels the energy is released in the form of radiations. this energy is exactly equal to the energy difference between the orbits. The characteristics bright colors are due to the these emitted radiations. These emitted radiations can be seen if they are fall in the visible region of spectrum.
Answer: a) 
b) 
c)
d) 
e) 
Explanation:
A balanced nuclear equation is one in which the atomic number and mass number remains same on both sides of the equation i.e the number of protons and neutrons remain same.
General representation of an element is given as:
Z represents Atomic number
A represents Mass number
X represents the symbol of an element
a)
b) 
c) 
d)
e)
31
A dalton is the same as an atomic mass unit. And an atomic mass unit is approximately the mass of a nucleon (proton or neutron) such that the mass is 1 g/mol. So in this problem you have 15 protons and 16 neutrons, so the number of daltons is 15 + 16 = 31.
