Which of the Following Are Radiation-Shielding Design Considerations

Which of the following are radiation-shielding design considerations?
1) The mean energy of the x-rays that will strike the barrier
2) Whether the barrier is of a primary or secondary nature
3) The workload of the unit
4) The use factor of the unit
5) The occupancy factor behind the barrier

A) 1,2,3,and 4 only
B) 1,3,4,and 5 only
C) 2,3,4,and 5 only
D) 1,2,3,4,and 5