Замените инфинитивы глаголами в present perfect, present in-definite, present continuous, present perfect continuous: 1. he (to solve) the cross-word puzzle for half an hour and he (to say) he (to be) about to finish it as he (to think) over the last word. 2. the actors (to rehearse) since early morning; now they (to go over) the first scene as they (not to be) satisfied
with their acting. 3. here you (to be) at last! i (to wait) for you for twenty minutes. you (not to be) ashamed? 4. she (to speak) over the tele-phone long enough, it (to be) time for her to stop talking. 5. since you (to keep) late hours this week you (to look) tired and worn out. 6. it (to snow) steadily the whole week and it still (to snow) if it (to go) on like this nobody will be able to
reach the camp. 7. at last you (to open) the door! i (to ring) for an hour at least, it (to seem) to me. 8. my watch (to keep) good time ever since the first repair. 9. they (to discuss) this questions ever since i (to be) here and they (not to come) to any definite conclusion yet. 10. the typist (to miss) several words as she (to talk) all the time. 11. the lecturer (to mention) this name
several times but i cannot remember it. i (to write) it down as soon as he (to mention) it again. 12. he (to work) at the language all the time and (to make) great progress. his phonetics (to be) perfect, only a slight accent (to remain)

1. he (has been solving) the cross-word puzzle for half an hour and he ( says)  he (is)  about to finish it as he (is thinking) over the last word. 2. the actors (have been rehearsing) since early morning; now they (are going over) the first scene as they (are not)  satisfied with their acting. 3. here you (are) at last! i (have been waiting) for you for twenty minutes. aren't you ashamed? 4. she (has been speaking) over the tele-phone long enough, it (is) time for her to stop talking. 5. since you (have been keeping) late hours this week you (look) tired and worn out. 6. it (has been snowing)  steadily the whole week and it is still (snowing). if it (goes) on like this nobody will be able to reach the camp. 7. at last you (have  opened) the door! i (have been ringing) for an hour at least, it ( seems) to me. 8. my watch (has kept) good time ever since the first repair. 9. they (have been discussing) this questions ever since i (am)  here and they (have not come)  to any definite conclusion yet. 10. the typist (has missed)  several words as she (has been talking)  all the time. 11. the lecturer (has mentioned)  this name several times but i cannot remember it. i (am going to write)  it down as soon as he ( mentions) it again. 12. he (has been  working) at the language all the time and (has  make)  great progress. his phonetics (is)  perfect, only a slight accent ( remains)

Некоторые факты из истории авиацииНаша страна-родина авиации. Первый российский самолет был построен А. Ф. Можайским в 1883 году. Это доказало возможность возведения более тяжелых, чем воздушные суда. Появилась новая наука-аэродинамика. Такие ведущие ученые, как Жуковский, Чаплыгин и Циолковский, проводили исследования в России. Они разработали разные теории. Эксперименты проводились в устройстве, известном как аэродинамический туннель.Авиация фактически развивалась после Октябрьской социалистической революции. Цельнометаллические самолеты, дальние бомбардировщики и высокоманевренные истребители были построены в первые годы.После Второй мировой войны последовали новые важные события. Поршневые двигатели были заменены реактивными двигателями. Они удвоили высоту и скорость самолетов и доказали возможность развития сети гражданских авиакомпаний.Сегодня самолеты могут безопасно летать в любую погоду и в любое время дня и ночи, ведь у них есть современные приборы. Пилоты могут использовать двустороннюю связь. Существуют также приборы для радионавигации в слепом полете.реактивный самолет обеспечивал быстрое развитие военной авиации. Современные военные самолеты могут преодолевать большие расстояния на больших скоростях.Продолжаются научно-исследовательские работы и эксперименты в области аэронавтики. В результате больших достижений в ракетостроении были построены космические аппараты и начались научно-исследовательские работы в космическом пространстве.

2. When you see... , tell ...

Poseidon got angry and decided to punish him