Ich bin jetzt so vorgegangen, bei beispielsweise b) had to unterstreiche und nicht "apply", da es noch im Infinitiv steht.
Ich bin mir bei dem Ganzen noch etwas unsicher und bräuchte eine Bestätigung, ob ich es auch hoffentlich richtig verstanden habe.
Put the following sentences into the past tense and underline the verb form.
a) You must not smoke in here.
…You were not allowed to smoke in here.
b) He must apply for a new passport.
…He had to apply for a new passport.
c) I have to give you a new one.
…I had to give you a new one.
d) You are not to wear those torn trousers.
…You were not to wear those torn trousers.
e) She won’t have to come again.
…She didnt have to come again.
f) They haven’t got to go back, have they?
…They didn´t have to go back, did they?
g) You needn’t listen to him.
…You didn´t have to listen him.
h) She has got high fever and mustn’t get up for a few days.
…She had gotten high fever and was not allowed to get up for a few days.
i) They fear that there may be a drastic rise in prices.
…They had feared that there might be a drastic rise in prices.