问题补充:
单选题Whenproductsmadeinfactories_____,e to an endB.are put to useC.are used upD.wear out
答案:
D解析wear out本题中意指(become useless form continued use of wear)用坏,穿破,如:The machine will soon wear out.(这机器即将用坏。)come to and end(结束),put ... to use(投入使用), use up(用完), come into use(开始投入使用)。