Which of the following is true about temporary stairs?

a. It's fine to use skeleton metal frame structures and steps for short-term work.
b. All treads and landings must be replaced when worn below the top edge of the pan.
c. Steps can have slightly different vertical rise if the height difference is less than 1 1/2 inches.
d. Temporary treads should be made of wire mesh to allow water or other liquids to drain.