The document discusses the differences between the modal verbs "must" and "should" as well as "must" and "have to". "Must" expresses strong obligation or necessity from the speaker's point of view, while "should" suggests something advisable. "Must" cannot be used for past obligations, where "had to" is used instead. "Have to" expresses objective obligation from an external source rather than personal views.

1. Should vs. Must Stores must give out recyclable plastic bags. We should use re-usable bags when shopping. The car industry must change engines that burn fossil fuels. We should select cars that are more fuel-efficient. We must protect our environment, or our resources will disappear. We should protect our environment. It makes good sense. We use must to express a stronger point of view. "We need to..." "We have to..." The modal must also expresses opinion, one person's point of view. We use should to suggest something. "It is advisable to..." The modal should expresses opinion, one person's point of view. MUST SHOULD

2. Must (subjective obligation) We often use must to say that something is essential or necessary (strong advice), for example: I must go. You must stay here Structure of Must Must is a modal auxiliary verb. It is followed by a main verb. The structure is: subject + must + main verb The main verb is the base verb (infinitive without "to"). Look at these examples:

4. In general, must expresses personal obligation. Must expresses what the speaker thinks is necessary. Must is subjective . Look at these examples : I must stop smoking. You must visit us soon. He must work harder . In each of the above cases, the "obligation" is the opinion or idea of the person speaking. In fact, it is not a real obligation. It is not imposed from outside .

10. We can use have to in all tenses , and also with modal auxiliaries. We conjugate it just like any other main verb. Here are some examples: it again. to do have may They modal (may) the time. to change had have We present perfect to wait. having is She present continuous tomorrow. to work have will I future simple today. to work have I present simple yesterday. to work had I past simple infinitive main verb have auxiliary verb subject

12. Angela, you ______leave your clothes all over the floor like this. 10 Bicyclists ______remember to signal when they turn. 9 Do you ________work next weekend? 8 You _______come if you don’t want to. 7 Your daughter may _____ try on a few different sizes. 6 If you are under 13 you ____ get your parents' permission. 5 We ______forget to take the chicken out of the freezer. 4 All employees ________be on time for work. 3 She will _____wait in line like everyone else. 2 Yesterday I_______ finish my Geography project.