卡车倒车和掉头的时候，我听见发动机的轰鸣声。I heard the engines revving as the lorries backed and turned.他们不时地听到大卡车的轰鸣声。Now and then they heard the roar of a heavy truck.听到发动机的轰鸣声，杰克猛地抬起了头。Jake's head jerked up at the throb of the engine...