`1`  I'm not sure about what we should to do

`+` To do `->` do 

`-` S + should + V-infinity `:` nên/cần làm gì đó 

`2` Are we going to must work overtime again this week?

`+` must `->` remove must

`-`  Chủ ngữ `+ S +` going to `+` V-infinity `?`

`3` We have many things to do this week, so I dont know if I can't go to English class.

`+` Can't `->` can

`-` `S +` not `+` know `+` if `+ S +` can `+ V`

`4` I have to thought about the problem for a while, but I finally figured it out

`+` Have to thought `->` had to think

`-` `S +` have to `+` `V :` cần làm gì đó 

`5` You should quiet in class; otherwise, your classmates cant concentrate

`+` Quiet `->` be quiet

`-` `S +` should `+` V`:` nên làm gì 

`1`. to do `->` do

`-` S + should + V-inf: nên làm gì

`2`. must `->` bỏ must

`-` TLG: Am/Is/Are + S + going to + V-inf?

`3`. can't `->` can

`-` S + not + know + if + S + can + V-inf

`4`. have to thought `->` had to think

`-` S + have to + V-inf: phải làm gì

`5`. quiet `->` be quiet

`-` S + should + V-inf: nên làm gì