What is an industry recommended best practice when placing and populating a rack of equipment?

A.
Place the heaviest items in the top, and populate items from the top to the bottom.

B.
Place the heaviest items in the bottom, and populate items from the bottom to the top.

C.
Place the heaviest items on the bottom, and populate items from the top to the bottom.

D.
Place the heaviest items on the top, and populate items from the bottom to the top.

Explanation:

Always plan the rack installation so that the heaviest item is on the bottom of the rack. Install the heaviest item first, and continue to populate the rack from the bottom to the top.
References: http://h10032.www1.hp.com/ctg/Manual/c01080450