What is the relationship between time and transportation infrastructure? (Select all that apply.) Replacement of parts of the transportation infrastructure could take decades. Many unscheduled delays result from interruptions in service. The time for replacing the existing infrastructure has already passed. Much of the existing transportation infrastructure is very old.

A)-in the process of engineering design, explain the contribution of material selection. b)- explain the procedure of synthesis as is employed in engineering design. c)- is there any relationship between ergonomics and engineering design? explain. d)- safety consideration in engineering design includes human, product and the enviroment . explain how safety will be incorporated into the design?