15. SHOULD- SHOULDN´T- MUST We use shouldtosuggestanobligation. He shouldspend more time in hishomework. Shouldn´tisusedtogiveanadvice. I thinkyoushouldn´tgoout becase itisraining. MUST Itisusedtoexpressnecessityorstrongobligation. Expressionsforordersancommands Youmustarriveearlytonight. Youmustbringyourhomeworktomorrow

16. . Writeshould, shouldn´t , mustormustn´twhereitcorresponds You ___________writeyourexerciseswithink. You ____________ smoke in a closedarea. You ____________ arivetoclasson time. Helen __________ see a doctor becausesheissick. You __________ finishyourworkbeforeyougo. We_________be more carefulwiththewater. We ________speak in English in cass. They __________speak in class. Carlos __________paytherenton time. The bus ____________arrive at o´clock.

17. FIRST CONDITIONAL The conditional sentences consist of two parts: The if – clause ( hypothesis ) , and the main clause. If he wakes up , he will miss the plane The first conditional express a real or very probable situation in the present or the future. The sentences not always begin with the if clause. He will miss the plane , if he wakes up.

18. IF - WHEN We use when in conditionals to show that we are sure that something will happen. I´ll see you when I come to Pachuca. We use if in conditionals to show that we are not sure whether something will or not happen. I´ll see you if I come to Pachuca.

19. too , too much , too many We use these words to say that something is more than we wanted. I´ll try not to get too late. He ´s got too much work to do. I´ve always got too many things to do.

20. Enough – not enough We use enough to say something is the correct number or amount. I have enough money to buy this car. I thing this flat is big enough for you and me. We use not enough to say something is less than we wanted. The baby isn´t old enough to talk. I don´t have enough money to buy the car.