Question

Students ___________ to wear uniforms, but they ___________ respect the property and equipment of the school and others. Every student _______be serious, honest, responsible, polite, and neat in appearance. In Japan, students _________ forget to sweep the hall floors before they go home at the end of the day. 

must / had to / have to / must

have / must / has to / mustn’t

has / must / have to / mustn’t

must to / mustn’t / has to / must

2- A babysitter _____ know that she/he _______ open the door if someone he/she does not know want to come in. If the person doesn’t go away, he’ll/she’ll ____________call the police.

must / mustn’t / has to

mustn’t / must / have to

have to / must / mustn’t

must / has to / has to

​

Answer 1

Resposta:

1- have / must / has to / mustn’t

2- must / mustn’t / has to

Explicação:

Answer 2

Resposta:

1-has / must / have to / mustn’t

2-Must, mustn't, has to.

O must é usando quando precisamos expressar um dever,uma obrigação ou se estiver na forma negativa uma proibição.

Na frase analisada, quem escreve deseja salientar que é um dever/obrigação da babá(babysitter) saber que ela não deve abrir a porta para alguém que ela não conheça, por isso usamos em seguida must not, que na sua forma contraída é mustn't.

Na última frase, podemos analisar que o verbo has to, tem a função de auxiliar o verbo "call". Usamos has to ao invés de have to pois estamos falando de uma pessoa apenas, no singular, apenas de uma babysitter.