GRAMMAR MODAL VERBS AND THEIR SUBSTITUTES Remember that modal verbs include can/could, may/might, must, shall/should, will/would, need. They are auxiliary verbs which are used with other verbs to express ability, permission, possibility, obligation, wish, and so on. They do not need an additional auxiliary in negatives or questions, they are invariable and they cannot be used in all tenses. There are substitutes for the tenses where they cannot be used. MODAL MEANING SUBSTITUTE can/could ability, permission (ability) to be able to may/might possibility, permission (permission) to be allowed to must obligation, strong belief (obligation) to have to (prohibition) not to be allowed to should/ought to advice to be supposed/expected to will/would request, offer to want need necessity, absence of obligation to have to 5 Complete these sentences with modals or their substitutes. Sometimes you have different options. 1. Beakers ............................ hold a variety of chemicals. 2. Hydrogen ............................ be the fuel of the future. 3. Drinking water containing pathogens ............................ be purified. 4. CFCs (not) ............................ rained out of the air. 5. ............................ I use your goggles, please? ACTIVITIES 6. We ............................ wear a lab coat when working in the lab. 7. You ............................ be more careful when handling acids. Excuse me, may I leave? You must be life forms microbes and I m supposed to be just a computer virus 8. Sorry I m late! I ............................ finish writing the lab report. 9. We ll ............................ work hard if we want to pass the exam. 10. I (not) ............................ use a spectrometer until my teacher helped me. 11. I m not sure I ll ............................ finish before the end of the lesson. 12. You ............................ be right but I m not sure. 13. This laboratory ............................ be over 30 years old. 14. She s ............................ repeat the experiment. 15. Let s be quick, I don t want to ............................ work late. 166 Module 4 ATOMS