All three are correct, but they have different meanings:
They could have learned — It was possible for them to learn
They should have learned — They had an obligation to learn
They must have learned — I am sure that they learned
10 de junio de 2023
0
0
0
must
9 de junio de 2023
0
0
¿No has encontrado las respuestas?
¡Escribe tus preguntas y deja que los hablantes nativos te ayuden!