`19.` All drivers must have a driving license.

`-` tobe obligatory: bắt buộc `->` must Vo: phải làm gì

`20.` People should have a visa to travel to India.

`-` tobe a good idea: `1` ý kiến hay `->` should Vo: nên làm gì

`21.` You don't have to shout because i can hear you perfectly well.

`-` tobe not necessary: không cần thiết `->` not have to Vo: không cần phải làm gì

`22.` Customers must go on the trips organized by the hotel.

`-` tobe obligatory: bắt buộc `->` must Vo: phải làm gì

`o` `Ley`

`19`  All drivers must have a driving license.
`->` must + V-inf: phải làm gì?

`20` People should have a visa to travel to India.
`->` should + V-inf: nên làm gì?

`21` You don't have to shout because i can hear you perfectly well.
`->` not have to: không cần phải làm gì?

`22` Customers must go on the trips organized by the hotel.
`->` must + V-inf: phải làm gì?