Must (have), Can't (have)

Regla fácil:

En este caso must (have) y can't (have) se utilizan para hablar de cosas de las que estamos seguro son verdad.

Ejemplo

English:

You've been traveling all day. You must be tired.

Español:

Has estado viajando todo el día. Debes estar cansado.

Ejemplo

English:

You just had dinner. You can't be hungry.

Español:

Acabas de comer. No puedes tener hambre.

Ejemplos

English:

The phone rang, but I didn't hear it. I must have been asleep.

Español:

El teléfono sonó pero no lo escuche. Debí haber estado durmiendo.

English:

Tom walked into the wall. He can't/couldn't have been paying attention.

Español:

Tom se dio contra la pared. No podía haber estado prestando atención.

Fórmula

Presente

Afirmativa

sujeto + must + verbo (infinitivo)

He must be tired after working all day.

Negativa

sujeto + can't + verbo (infinitivo)

He can't be tired, he only worked for an hour.

Fórmula

Pasado

Afirmativa

sujeto + must + have + been + verbo (infinitivo)

He must have been tired after working all day.

Negativa

sujeto + can't/couln't + have + been + verbo (infinitivo)

He can't/couldn't have been tired, he only worked for an hour.