Read the selection and choose the best answer to each
question.
Under the Sea
by Michael Signal
1 Some scientists claim that we know more about the far reaches of space than the depths of Earth's oceans. Exploring the oceans proves to be a difficult task because, like space, the ocean is a very inhospitable environment. Humans can only dive for brief periods of time and at shallow depths, without protection. Submarines, diving suits, and SCUBA gear help ocean explorers understand more about the oceans, but diving beneath the waves is still dangerous work.
2 Inventors built the first submarines in the 1600s. Some early submarines used breathing tubes to get air from the surface. Many of the first submarine designs didn't even work. Today, some submarines can dive more than four miles below the water's surface. Nuclear submarines can stay submerged indefinitely. They only have to resurface if the crew runs out of food. But, even with great technical advances, there are still parts of the ocean that submarines cannot reach.
3 Divers could not explore the undersea world closely from inside of a submarine. Diving suits started to appear in the 1700s. They were very crude. The first diving-dresses, as they were called, consisted of leather jackets or vests, and large, round metal helmets. Air was usually supplied through a hose from the surface. Modern diving suits can take divers thousands of feet below the surface. They can be equipped with electric lights, cameras, and built in propulsion systems. Modern diving suits can help ocean explorers have engaging, hands-on trips under the sea.
4 SCUBA suits are different from traditional diving suits. SCUBA stands for selfcontained underwater breathing apparatus. The most important pieces of SCUBA gear are the oxygen tank and oxygen regulator. SCUBA divers wear tanks full of compressed oxygen. Divers cannot breathe the pressurized oxygen, so the oxygen regulator reduces the pressure so that it is safe to breathe. A SCUBA diver doesn't get an air supply from the surface. SCUBA divers can wear thin, tight wetsuits to keep them warm. SCUBA equipment offers more freedom than diving suits, though diving suits can submerge much deeper.
5 Scientists, explorers, and curious people have wondered about the world beneath the sea for centuries. With submarines, diving suits, and SCUBA gear, people can learn a lot about underwater environments. We still have much to learn about the oceans and what is beneath them. As diving equipment improves, we will continue to learn more.