23. PERATURAN (OBLIGATION) menggunakan modals: must, have to, ouhgt to + VERB 1

*MUST = artinya HARUS , utk menegaskan suatu peraturan yg mutlak dipatuhi, jika dilanggar ada sanksinya

        Contoh: You MUST wear uniform to school.

                        You MUST use helmet when riding motorcycle.

*HAVE TO atau OUGHT TO = artinya harus, namun tidak menimbulkan sanksi tegas

        Contoh: I’m sorry I have to pick my mother at the mall.

                        Excuse me we ought to be on time to the meeting.