A father and son lived on a mountain, and every day they had to drive an ox cart down the mountain to sell firewood. The father, being more experienced, would take charge of driving the cart. The mountain road was rugged with many sharp turns. The son, with his keen eyesight, would always alert at the turns: "Dad, it's time to turn!"
One day, the father was unable to go down the mountain due to illness, so the son drove the cart alone. When they reached a bend in the road, no matter what methods he tried - pushing, pulling, or even tempting the ox with green grass - the ox wouldn't turn. Puzzled by the situation and after much thought, the son finally came up with one solution. Looking around to ensure no one was nearby, he leaned close to the ox's ear and shouted loudly: "Dad, it's time to turn!" Upon hearing this, the ox responded immediately and turned as instructed.