1 Head-on collision with Car C threatens you, in Car A, after you have pulled out to pass Car B on two-lane highway. Best solution (1) is to brake hard, let B go ahead, then tuck in behind.
2 Risky solution is to accelerate decisively (2), sound horn, and try to pull ahead of B, who by then should be slowing fast. If B maintains speed you may have to risk forcing him off road.
3 Disaster course would be to swing left (3), closing C's natural escape route and probably insuring a crash either with you or B. The emergency, of course, should never have been provoked.