English grammar
Must be, will be, could that be: guessing
Guess how someone feels or what they're doing now with must be / could that be.
From the scene They must be so tired!
In short
Guess about now with must be when you're fairly sure, or that'll be. Ask with Could that be…?
Your turn
Which one goes with must be + age / number?
Options: They must be resting on every floor. · She must be about eighty. · They must be so tired!
Show answer
must be + age / number → She must be about eighty.
How it works
To guess about right now, use must be when you're fairly sure: they must be tired.
Your turn
Pick the word that fits the line.
And Doña Elena (blank) be about eighty, right?
Options: might to · musts · must
Show answer
And Doña Elena must be about eighty, right?
Y Doña Elena tendrá unos ochenta años, ¿no?
Good to know
That'll be… is another confident guess (about now, not the future). To ask, use could: Could that be my mum?
Your turn
Pick the word that fits the line.
At this time? They (blank) be hungry, poor things.
Options: must · are must · musting
Show answer
At this time? They must be hungry, poor things.
¿A estas horas? Tendrán hambre, pobres.
must be (fairly sure) They must be so tired!
Nuria
They must be so tired! Fourth floor, and no lift.
¡Qué cansados estarán! Cuarto piso, y sin ascensor.
Your turn
What fills the gap?
(blank)! Fourth floor, and no lift.
Options: They must be resting on every floor · They must be so tired · She must be about eighty
Show answer
Nuria
They must be so tired! Fourth floor, and no lift.
¡Qué cansados estarán! Cuarto piso, y sin ascensor.
must be + age / number She must be about eighty.
Your turn
What goes with She must be about eighty.?
Options: must be + age / number · must be (fairly sure) · must be + -ing (happening now)
Show answer
She must be about eighty. → must be + age / number
must be + -ing (happening now) They must be resting on every floor.
question: could that be…? Could that be my mum?
Javi
I hear footsteps. Could that be my mum?
Oigo pasos. ¿Será mi mamá?
Your turn
What fills the gap?
I hear footsteps. (blank)?
Options: She must be about eighty · Could that be my mum · They must be so tired
Show answer
Javi
I hear footsteps. Could that be my mum?
Oigo pasos. ¿Será mi mamá?
that'll be… (confident guess) That'll be Doña Elena.
Common mistake
Not mustn't or can't here. A confident guess about now.
They must be so tired! Fourth floor, and no lift.
¡Qué cansados estarán! Cuarto piso, y sin ascensor.
Practise it in the story
Meet this rule inside a short animated scene. Answer as it plays, then say the lines yourself.
Practise free in the appSee all forms
| must be (fairly sure) | They must be so tired! |
|---|---|
| must be + age / number | She must be about eighty. |
| must be + -ing (happening now) | They must be resting on every floor. |
| question: could that be…? | Could that be my mum? |
| that'll be… (confident guess) | That'll be Doña Elena. |
More lines from the story
- JaviAnd Doña Elena must be about eighty, right?Y Doña Elena tendrá unos ochenta años, ¿no?
- NuriaAt this time? They must be hungry, poor things.¿A estas horas? Tendrán hambre, pobres.
- NuriaEighty. And she climbs faster than me!Ochenta. ¡Y sube más rápido que yo!
- JaviOr Doña Elena must be telling them everyone's life story.O Doña Elena les estará contando la vida de todos.