---The boys have had a long friendship. 这些孩子们有很长时间的友谊了
--A good map would be a help. --It was a relief to sit down. -- He had a good knowledge of mathematics.
某些物质名词或抽象名词用作复数时,词义往往起变化。 例如: --Light(光)travels faster than sound. --The lights(灯)are on. --He is a teacher of five years' experience(经验). --He is relating to us his experiences(经历)as an explorer