I wonder which one to choose here:
- My father should drive carefully when it’s raining.
- My father has to drive carefully when it’s raining.
closed as not a real question by MετάEd, kiamlaluno, Kris, RegDwigнt♦ May 14 '13 at 9:13
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Both are correct but they mean different things.
Have to is the paraphrase for must, another modal auxiliary verb.
The usual periphrastic constructions for should are supposed to (pronounced /spostə/)
In the sentences offered,
(1) means that my father really ought to drive carefully under those circumstances
(2) means that driving in the rain is difficult for him and forces him to drive carefully.
In (1), my father is responsible for his driving and may or may not comply.