Help the amateur detective solve the Great Pizza Mystery by choosing the correct deduction.

Liam _____ the last slice of pizza because he was visiting his grandmother in another city all weekend!

The correct answer is can't have eaten.

We use can't have + past participle to express strong certainty that something in the past was impossible. Since Liam was in another city, it is logically impossible for him to be the pizza thief!

Must have expresses certainty that something did happen, while might have only shows a possibility. Shouldn't have is used for regrets or criticism, not deduction.