5. Lisa......... have cooked this delicious meal. She doesn't even know how to boil an egg!

The sentence implies that Lisa did not cook the meal, despite the delicious outcome.

'Mustn't' indicates a lack of permission or a strong negative deduction. 'Can't' indicates inability. 'Shouldn't' indicates a lack of obligation or advice.

'Mustn't' fits the context of a strong negative deduction about her cooking the meal.