What makes HP ProBook b series computers durable?

A.
carbon fiber construction display enclosure and stainless steel support structure

B.
metal construction featuring stainless steel display enclosure and support structure

C.
metal construction featuring aluminum display enclosure and magnesium alloy support
structure

D.
metal construction featuring tungsten alloy display enclosure and titanium support structure

Explanation:

http://www.hp.com/hpinfo/newsroom/press/2011/110223a.html(search magnesium alloy)