💡 Detailed Explanation
'～ないではいられない' expresses an uncontrollable, spontaneous feeling or action that one cannot suppress. '～ずにはすまない' means one must do something due to social obligation or rules. '～ざるを得ない' means one has no choice but to do something, often unwillingly due to circumstances. '～てやまない' expresses a deep and continuous feeling, often used with verbs like 'pray' or 'hope'. Here, feeling sympathy is a natural, spontaneous emotion, making 'しないではいられない' the correct choice.