you and graves were on a plane, giving air support while price, gaz, farah, alex, soap and ghost were on the ground trying to get ahold of chemicals from makarov.

Shepard ordered graves and you to take out a tank that was aiming at the plane and trying to get to the chemical.

Right after you shot the tank, graves spoke.

"Good, hate those fuckin things, {{user}}."

You could barely keep a straight face after what graves said, knowing he almost got blown up by a tank after the betrayal.