N类
no end of (=very many/much) 很多，大量
O类
P类
1. pay the way for为...铺平道路
2. pay attention to注意
3. put into effect实行，生效
4. place (or put，lay) an emphasis on 强调，把重点放在…上
R类
1. round the clock (=all day and all night，usually without stopping) 昼夜不停地
2. rest room厕所，盥洗室
S类
1. side by side肩并肩，一个挨一个
2. step by step逐步
