Use hardline and keep getting a two killstreak after you get a two kilstreak kill yourself then do it again, it's quite simple.
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The UAV shows enemies on your in-game map as red dots unless they have the perk cold-blooded on.
itdepends on the map but i think heartbeat sensor is awesome but some people get ninja perk so they cant be seen by it
hmm... UAV, Care Package, Counter UAV, Predator Missile, Sentry Gun, Precision Airstrike, Attack Helicopter, Harrier Strike, Emergency Airdrop, Stealth Bomber, Pavelow, AC130, Chopper Gunner, EMP, And TACTICAL NUKE
Heartbeat is definitely the way to go. First, UAV only lasts for a little while, 30 seconds I think; although it works all across the map. However, heartbeat sensor is always working. And although it has a smaller range, it never runs out.
In order to complete the cluster bomb challenge, you have to kill 5 enemies with a single air strike. I suggest using the stealth bomber with UAV for this. A recommended game type would be ground war.