That noise... It ___ be a ghost. Ghosts aren't real.
can't
About the party, Maybe i'll be able to go. / I ___ be able to go.
might/may
Oh! That ___ be Dave, he said he was almost here.
must
This cellphone ___ be Julia's. Hers is red.
can't
Roger didn't come to class. Perhaps he's sick. / He ___ be sick.
might/may
She looks amazing. She ___ be a model.
must
Caith is not here yet, maybe she forgot the time. / she ___ have forgotten the time.
might/may
That guy ___ be a local. He doesn't look Mexican.
can't
They look really cute together. They ___ be a couple.
must
Danna is late. She's probably stuck in traffic. / She ___ be stuck in traffic.
could
Those guys are dressing funny. They're probably going to a party. / They ___ be going to a party.
could
That woman seems worried. It's posible she's lost. / She ___ be lost.
could