The best place to get Chain A,B, and C is at the beginning of the 11th mission. The name of the mission is Hawk Eyes – The Escort. In this mission you are the gunner an impenetrable attack helicopter with unlimited ammo and missiles. About 30 seconds into the mission you will come to a small village. You will hear your character telling his convoy not to enter the village because it is full of enemies. You’ll see 3 small groups of insurgents on the ground, DON'T KILL THEM YET. Wait till the chopper circles the village, and about 4 enemies run from behind a truck on the top right side. Shoot 1 missile at the truck, 1 to the left of the enemies in the street, and your last missile at the group in the building on the left, then use your gun and finish the last 3-4 on the right side. If the bottom right multipliers says x10 or more you know you did it. If not restart but I did it first try so you should be able to as well.