1. The visitors are here at last. They have arrived.
2. Mark's car isn't blocking us in now. He has moved it.
3. We haven't got any new videos. We are watching all these.
4. The teacher always gives us interesting project work.
5. Let's go inside now. It is beginning to rain.
6. The children go swimming every day.
7. We're trying to catch the ball that is rolling down the hill.
8. I haven't done my homework yet.
9. Have you sent aunt Mary a birthday card yet?
10. Nalini hasn't heard from his brother for two months.
11. We have had a lot of work to do recently.
1. The invention of the railroads began with the invention of the steam engine, the idea of which originated many years earlier. James Watt's improvement on the Newcomen's engine allowed the steam engine not only go up and down, but to turn gearwheels. 2. In 1781 Watt designed and produced a rotary-motion steam engine. This new engine could be applied to many different types of machinery. 3. In 1804 Richard Trevithick, an English engineer invented a steam locomotive, and his invention brought together the idea of iron rails and the steam engine. 4. In 1882 Edison installed the first durable electric lights in his own labs, and later built the first public power station. However, Edison's DC current system had only a three-mile range.
