用括号内所给单词的适当形式填空。
—Could you tell me_ it's polite to eat noisily in Japan, Kumiko?
—Sure! It's polite to do that. It means you like the food very much.
①要学法、懂法、守法
②受害者要学会自我保护
③欺凌者的行为是一种违法行为
④校园欺凌现象是正常的