Unlike Call of Duty: Modern Warfare 2, you won't be getting the pro version of a perk by completing a challenge. In Call of Duty: Black Ops you need to complete a set of 3 challenges in order to get the pro version of the perk. These are the challanges you need to complete to get lightweight pro:
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The Lightweight pro perk allows you to sprint faster. The lightweight pro perk allows you to aim faster after sprinting.
you get extra mags as you get in modern warfare 2,too.
most likely from the scavenger pro
use the perk 'warlord' or 'warlord pro' to get multiple attachments.
quick aim after sprinting