For most of them, seven to eight hours a night is (24)_____, but some sleep longer, while others manage with only four hours.

In 1959, the government of Egypt was working on a plan to build a dam on the River Nile. It was called the Aswan Dam, and it was intended to generate electricity and allow the river water to be used for agriculture. There was one big problem with the plan, though. The dam would flood a nearby valley that contained ancient Egyptian treasures, including two enormous stone temples.

It can be difficult for governments to choose culture and history over economics. However, if countries always made decisions like this, the majority of the world's ancient sites would end up being destroyed. Luckily, UNESCO stepped in. They formed a committee that tried to convince Egypt to protect its ancient treasures. With support from many countries, they were finally successful. The huge temples were carefully removed from their original site and moved to a safe location so that the dam could be built.

After their success in saving the temples in Egypt, UNESCO went on to save more sites around the world. They protected lagoons in Venice, ruins in Pakistan, and temples in Indonesia. With industrialization changing the world rapidly, there were many sites that needed to be saved. Eventually, UNESCO formed the World Heritage Organization to protect important natural and historic sites wherever it was necessary.

By now, the World Heritage Organization has protected hundreds of sites ranging from beautiful natural islands to buildings in large cities and ancient ruins. If you're able to visit any of the many protected sites, you'll agree it was worth it.

Deep sleep is important for everyone. The actual amount of sleep depends (23)_____ your age. A young child ought to sleep ten to twelve hours, and a teenager about nine hours. Adults differ a lot in their sleeping habits. For most of them, seven to eight hours a night is (24)_____, but some sleep longer, while others manage with only four hours.

For a good night, having a comfortable (25)_____ to sleep is very important. Also, there should be (26)_____ of fresh air in the room. A warm drink sometimes helps people to sleep, although it is not a good idea to drink coffee immediately before going to bed.

If you have to travel a very long distance, try to go to bed earlier than usual the day before the journey. This will help you to feel more (27)_____ when you arrive.

One of the (A) most important tasks (B) of parents is to teach (C) their kids to live independent(D).