N類
    no end of (=very many/much) 很多，大量
    O類
    P類
    1. pay the way for為...鋪平道路
    2. pay attention to注意
    3. put into effect實(shí)行，生效
    4. place (or put，lay) an emphasis on 強(qiáng)調(diào)，把重點(diǎn)放在…上
    R類
    1. round the clock (=all day and all night，usually without stopping) 晝夜不停地
    2. rest room廁所，盥洗室
    S類
    1. side by side肩并肩，一個挨一個
    2. step by step逐步