Resposta:
a) Sarah walked to school yesterday.
N: Sarah didn't walk to school yesterday.
I: Did Sarah walk to school yesterday?
b) We talked to the teacher in the morning.
Ni We didn't talk to the teacher in the morning.
I: Did we talk to the teacher in the morning?
c) My friend Tom studied Math yesterday.
N: My friend Tom didn't study Math yesterday.
I: Did my friend Tom study Math yesterday?
Agora, lembrando que:
-> Os verbos do passado no inglês precisam terminar com "ed" (como o verbo to walk que se transformou em walked);
-> Como estamos falando de negativas e interrrogativas, usamos o did e o did not (ou didn't, que é a forma abreviada);
-> Esse did vai simplesmente substituir o "ed" do final do verbo, então não será preciso usar;
-> Quando fazemos uma pergunta, o Did fica no início da frase (como: "Did Sarah walk to school yesterday?")
-> Já quando for uma forma negativa, vai vir depois do sujeito (como: "Sarah didn't (did not) walk to school yesterday)
Espero ter ajudado :)
