用适当的介词填空.We should wash our hands ( ) meals.I often ask Mr Zhang ( ) some science problems.

问题描述:

用适当的介词填空.
We should wash our hands ( ) meals.
I often ask Mr Zhang ( ) some science problems.

同意上一位的说法。before about

before:在吃饭之前;
about:关于一些科学问题