This rule explains why when in English, the phrase "John is talking to Lucy" is turned into a question, it becomes "Who is John talking to?", and not "John is talking to who?".
Aturan ini menjelaskan kenapa dalam bahasa Inggris, saat frasa "John is talking to Lucy" berubah menjadi sebuah pertanyaan, menjadi "Who is John talking to?", dan bukan "John is talking to who?".