When You Are About to Couple a Tractor 5th Wheel

When you are about to couple a tractor 5th wheel to a trailer upper coupler,which of the following must be true?

A) trailer bolster plate should be about 1-inch higher than 5th wheel plate
B) trailer bolster plate should be about 1-inch lower than 5th wheel plate
C) 5th wheel jaws should in their closed position
D) 5th wheel secondary lock should be in latched closed position