Fill in the blanks with the correct modal
It _____ our baby who cried continuously all night since he was sleeping inside with us

can't have been

The correct modal to fill in the blank is can't have been.

The modal can't have been is used to express certainty about something that could not have happened. In this case, the speaker is certain that the baby could not have been the one who cried continuously all night because the baby was sleeping inside with them.

The other options are incorrect.

• Might not be is used to express possibility. In this case, it is not possible for the baby to have been the one who cried continuously all night.
• Shouldn't be is used to express a strong suggestion or advice. In this case, the speaker is not suggesting that the baby should not have been the one who cried continuously all night.
• Won't have been is used to express certainty about something that will not happen. In this case, the speaker is not talking about something that will not happen.