Students are allowed to stay away from school if they  (not want) to have classes that day. Teachers  (not tell) the students what to do on this or any other day.You can see a student who plays and  (not study​

1. Aren’t wanting.
2. Aren’t telling.
3.Don’t study’s.

1. Do the engineers carry out the experiments with new building materials?
2. Will the electronic computer make our travel in high speed train safer?
3. Are chemists developing new materials at present?
4. Was the first railway in our country electrified in 1926?
1. The engineers do not carry out the experiments with new building materials
2. The electronic computer will not make our travel in high speed train safer
3. At present chemists are not developing new materials
4. The first railway in our country was not electrified in 1926.

If you ring) me up, I shall tell you a secret. 2. If you were a poet, you would write beautiful poetry. 3. If he did not read so much, he wouldn't know literature so well. (?)4. If he had come to our house yesterday, he would have met his friend. 5. If he doesn't pass his examination, he will not get a scholarship. 6. If she hadn't helped me, I should have been in a very difficult situation. 7. My father would have more free time if he hadn't read) so many newspapers. 8. If only you had let me know, I would have gone there immediately. 9. If I were a famous singer, I would get a lot of flowers every day. 10. If you don't buy coffee, we shall drink tea. 11. If he is free tomorrow, he will certainly come to our party. 12. My brother would not have missed so many lessons if he hadn't hurt his leg. 13. If my friend had worked in my office, we should have met every day. 14. If you spoke English every day, you would improve your language skills. 15.If you get a "five", your mother will be happy. 16.If she had returned earlier, she would have been able to see him before he left. 17. If these shoes were not too big for me, I would buy them