孩子写 "I go to school with bus"，听着就别扭。正确说法是 by bus。by、with、for、from 这四个小词，看着简单，搭配全是坑。
by：乘交通工具、通过方式
- by bus / by train / by plane / by bike
- 但 on foot（走路）是例外，不用 by
with：用工具、和某人一起
- write with a pen 用钢笔写
- cut it with a knife 用刀切
- play with my friends 和朋友玩
for：为了、给
- a gift for you 给你的礼物
- buy a book for mom 给妈妈买本书
- thanks for your help 谢谢你的帮忙
from：从、来自
- I'm from Chengdu. 我来自成都。
- a letter from my pen pal 笔友来的信
- be different from 与……不同
几个固定搭配别换
- be good at 擅长
- be afraid of 害怕
- listen to 听
- wait for 等
一句口诀：by 交通 with 工具，for 对象 from 出处；固定搭配别乱换，多读几遍自然熟。
