They're all accelerating but B is at rest
Discussion
Correct, A acceleration forward, C acceleration backwards.
Diginostr:npub1wamvxt2tr50ghu4fdw47ksadnt0p277nv0vfhplmv0n0z3243zyq26u3l2 rE C'O'mpilE*****
He's probably refering to the counterintuitive "helium balloon in a truck"- riddle.