i don't know (what to say or do)/(what to say and to do)选哪个?为什么?

i don't know (what to say or do)/(what to say and to do)选哪个?为什么?
i don't know (what to say or do)/(what to say and to do)选哪个?为什么?

i don't know (what to say or do)/(what to say and to do)选哪个?为什么?
i dont know what to say or do.
否定句里面,and 通常转化为or
do 前面的to,与第一个to重复,因此可以省略

what to say or do
感觉是.

I don't know what to say and what to do```

I don't know what to say.
I don't know what to do.
固定搭配