Vamos analisar cada uma das alternativas para identificar a que utiliza corretamente a forma Contínua Passada dos Modal Verbs: a) They should have been finishing the report last week, but they were still working on it yesterday. - Correta. A estrutura "should have been finishing" está correta, indicando uma ação contínua no passado. b) They must have discussing the project when we walked in. - Incorreta. A forma correta seria "must have been discussing". c) He could have been traveled when we were trying to reach him. - Incorreta. A forma correta seria "could have been traveling". d) You should have studied for the exam while your friends were out. - Incorreta. Esta frase não usa a forma contínua. e) He must been working late since his office light was on when I passed by. - Incorreta. A forma correta seria "must have been working". Portanto, a alternativa correta que utiliza a forma Contínua Passada dos Modal Verbs é: a) They should have been finishing the report last week, but they were still working on it yesterday.