Examine the following statements ___________?

1. Factor of safety for steel should be based on its yield stress,
2. Factor of safety for steel should be based on its ultimate stress,
3. Factor of safety for concrete should be based on its yield stress,
4. Factor of safety for concrete should be based on its ultimate stress.
The correct statements are
A. (1) and (3)
B. (1) and(4)
C. (2) and (3)
D. (2) and (4)