为什么trees、boys、cows等词中的s是发/z/音,而cups中的s是发/s/音呢?

为什么trees、boys、cows等词中的s是发/z/音,而cups中的s是发/s/音呢? Boys In The Trees 歌词 对划线部分提问：Many boys can climb trees.划线部分是：climb trees only boys aloud 为什么出名 苹果树翻译起来是apple trees.为什么不是apples trees? Trees produce oxygen,为什么不是Trees provide oxygen trees look,the boys _____(collect) water from the riverto water the youny trees 一题英语完形填空.() the trees （）some birds .Can you () three boys underthetrees “Those boys chat under the trees all time.”中哪里错了是一般现在时. boys的复数词 几道大学英语单选题,请给详解And ___ them___one of their own or just a piece of wood.A.replace ;with B.substitute;byFruit trees were raided in the night and cows milked.A.out B.dryFruit trees were raided in the night and cows milked____. What ______ Mike do on the farm?He ________ cows.(milk)为什么说出其原因 the boys planted some trees on the hill yesterday.改为同义句 some trees — — on the hill by ththe boys planted some trees on the hill yesterday.改为同义句some trees — — on the hill by the boys yesterday 分析（语法结构、句意等各方面）Which of the two cows ___that___ you keep produces more milk? 英语翻译为什么用英语翻译张雨生是Backstreet Boys Three boy students为什么不用boys 英语词汇辨析题目jungle woods trees vines undergrowth 等