Three ways to ask a question in French: rising intonation (spoken), est-ce que (neutral), and subject-verb inversion (formal/written). Add quel/quelle/quels/quelles and the qu- words (qui, quoi, où, quand, comment, pourquoi, combien) to make information questions.
Yes/no questions: (1) Intonation — Tu viens ?; (2) Est-ce que — Est-ce que tu viens ?; (3) Inversion — Viens-tu ? (always a hyphen). Information questions: question word + est-ce que + subject + verb (Où est-ce que tu habites ?), or question word + inversion (Où habites-tu ?), or question word + verb + subject in casual word order (Tu habites où ?). Quel: agrees with the noun — quel (m.sg.), quelle (f.sg.), quels (m.pl.), quelles (f.pl.). -t- euphonique: when inversion creates a vowel clash (il arrive → arrive-t-il), insert -t-.
Which question form is correct?