Quiz playing is a wonderful way to increase your knowledge of English as a Second Language. Remember that all of our ESL quizzes have titles that are both friendly and technical at the same time… In the case of this quiz you might like to tell your friends about “Must You?” but no doubt your teachers will talk about the “Obligations quiz”! If you hear a technical term and you want to find a quiz about the subject then just look through the list of quiz titles until you find what you need.
If an English speaker wants someone else to stop doing something (maybe thoughtless, and/or repeated) that is annoying them - like swinging their feet back and forth under a seat, and banging it every time - they may simply ask: 'Must you?' (i.e., 'Do you absolutely have to keep on doing that?').
There are a surprising number of 'shades' of obligation in English: we 'must' balance our finances and we 'must' 'keep calm and carry on', etc..
How strong are you at knowing the best way to phrase these obligations?
The Instructor who prepares you for the Test might use any of these other three ways of explaining this to you.
Answer 1 slightly suggests that the Examiners are supposed to fail candidates who make this mistake ... but that perhaps, very occasionally, they might overlook it (please don't bank on this!).
Answer 2 is a simple paraphrase of No.4; Answer 3 is a declaration of the straight fact that if you touch the kerb, you will fail.