他已经在擦汽车轮毂了。He was already buffing the car's hubs.我在前后轮毂上都抹了润滑油，还调校了刹车。I greased front and rear hubs and adjusted the brakes.轴和轮毂通常用键固定在一起.Shafts and hubs are usually fastened together by means of keys....
Fat is an excellent insulator against the cold.脂肪是极好的抵御寒冷的绝热体。Dry air is a good insulator, but sea water is not.干燥空气是一种好绝缘物, 海水则不是.The atoms of an insulator hold their electrons very tight.绝缘体的原子把电子抓得很牢....
She is wearing tight, black leggings and a baggy green jersey.她身穿黑色紧身裤和一件宽松的绿色针织套衫。Outstanding dairy Breeds include the Holstein, Guernsey, Jersey, Ayrshire, and Brown Swiss.优良的乳牛品种包括好斯敦牛 、 根西牛 、 泽西牛 、 亚尔夏牛和瑞士褐牛.They wer...