they know what a good thing is and what a bad thing 是什么意思

they know what a good thing is and what a bad thing
他们所知道的一件好事是什么坏事
双语对照
例句:
1.
How do you know what are good vitamins and what are not?
你这么知道什么营养补充品是好的还是坏的？

2.
Most running stores have well-educated sales people thatknow what's good, what's bad and what's going to help yousurvive.
大多数跑步用品商店的售货员都有较强的专业知识，他们知道哪些是好的，哪些是差的，哪些有助于跑步。