Mark the correct alternative.

Marque a alternativa correta. 

A) We had better not to call him today.  We had better not call him today. Incorreta.

B) I ought to read this book, oughtn't I? Correta.

C) John is eighteen, so his sister must to be twenty. Não se coloca "to" após o modal "must".
John is eighteen, so his sister must be twenty.Incorreta.

D) I suggested she added this book to the list, and she finally would.  Errada. "suggested" está no passado, portanto, o auxiliar a ser usado é o "did".  I suggested she added this book to the list, and she finally did. Incorreta.

E) Last year I lived with my boyfriend but I knew I can live with my parents again at any time.  Errada.
 Last year I lived with my boyfriend but I knew I could live with my parents again at any time. Incorreta.

Gabarito do Professor: B

a) o verbo não deve vir no infinitivo, no caso, usando o "to". Da mesma forma com o "must" da letra C

O correto da E seria usar o "could" (poderia)

Neg+positive

A. We had better not call him today.

B. I ought to read this book, oughtn’t I?

C. John is eighteen, so his sister must be twenty.

D. I suggested her adding this book to the list, and she finally did.

E. Last year I lived with my boyfriend but I knew I could live with my parents again at any time.