Автор сделал несколько ошибок в употреблении Past Tenses в следующей шутке ему найти их и исправить. Once a mother and her two daughters were visiting London. They did sightseeing for some time when they came to the building with a noticeboard «National Picture Gallery» on it. The girls wanted to go in for they never were in any picture gallery. But their mother visited a picture gallery in her childhood and knew what it was like. She explained to the girls that there were no «real pictures» (movies she meant), but mere paintings.

Once a mother and her two daughters were visiting London. They had been sightseeing for some time when they came to the building with a noticeboard «National Picture Gallery» on it. The girls wanted to go in because they had never been to any picture gallery. But their mother had visited a picture gallery in her childhood and knew what it was like. She explained to the girls that they wouldn't see any «real pictures» (movies she meant), but only paintings.

Объяснение:

When I (rang) up my friend, he (was sleeping).When grandfather (was watching) TV, he (fell) asleep.When my friend (came) to see me, I (was doing) my homework.When I (was going) to the stadium, I (met) Kate and Ann.When Nick (rang) me up yesterday, I (was helping) mother.When the children (were walking) through the wood, they (saw) a fox.When I (came) home, my sister (was washing) the floor.When Mike (was playing) in the yard, he (found) a ball.When I (was drawing) yesterday, I (broke) two pencils.When I (met) Tom, he (was going) to the shop.When I (looked) out of the window, the children (were playing) hide-and-seek.I (went) to the theatre yesterday.At seven o'clock yesterday I (went) to the theatre.What you (did) at 5 o'clock yesterday? -I (was playing) the piano.When I (came) to school, the children (were standing) near the classroom.We (were playing) in the yard the whole evening yesterday.When I (was preparing) breakfast in the morning, I (cut) my finger.Last year I (went) to the United States. Did you go to Great Britain last year? - No, I (went) to France.What you (did) yesterday? — I (was translating) a very long article

The world of science doesn't have a bordres. We live in a world where discoveries are make constantly. There are many scientists . For example The great law of gravitation was discovered by Isaac Newtone. Radio was discovered by Alexander  Popov. Russian chemist Mendeleev invented the Periodic Table of Elements in 1869. Every time when scientists make discoveries we understand that we are just a speck in the huge world. The more of discoveries, the more questions. Consequently the world of science doesn't have a borders.