Explanation:

- Below the belt is an idiom that means something is cruel and unfair. It originates from boxing, where hitting below the belt is an illegal and unfair tactic.

- Option 1: Without any effort—This means achieving something easily, without putting in much work. It's not related to the idiom.

- Option 2: Very quickly—This describes doing something fast. Again, it doesn't fit the idiom's meaning.

- Option 3: Cruel and unfair—This accurately captures the essence of the idiom, referring to actions that are not only unkind but also unjust.

- Option 4: Suspiciously—This implies doubt or mistrust. It doesn't align with the idiom.