Which process causes hillsides and mountains to gradually get smaller?

Ibelieve the answer is b) aerosol inhalation may lead to heart attacks.

Decreased genetic variation is the answer. 

Ibelieve this is the answer:     evolution has no "goal". it is "simply" the survival of the fittest under a given condition. what should be the advantage of living longer? getting kids (=spreading the own genetic information) is done latest until the mid-40s after that we have not much biological meaning.  in addition,  not only does evolution not have a "goal," evolution doesn't necessarily mean "make us better! " it's absolutely possible to evolve negative traits.    hpe i could : )