財布に百円___ありません。
Q. Which particle means 'only (100 yen)' and requires the negative?
Translation
I have only 100 yen in my wallet.
Explanation
しか always pairs with a negative predicate and emphasizes scarcity: 百円しかありません 'no more than 100 yen'. だけ also means 'only' but takes an affirmative (百円だけあります), so with ありません the correct choice is しか.