What do you know about the sea? You may have seen it. Some of us have swum or bathed in it. It looks beautiful on a fine sunny day and it can be very  _ when there is a strong wind. What other things do we know about it? Of course, the sea is very large. In the world there is more sea than land. The sea covers three quarters of the earth. The sea is also very deep in some places. It is not deep everywhere, some parts of it are very great. At one spot, near Japan the sea is nearly 11 kilometers deep! Just think of it, the highest mountain in the world is only about 9 kilometers high! If you have swum in the sea, you know that the water is salty. Rivers carry salt from the land into the sea. Some parts of the sea are more salty than other parts. Do you know the Dead Sea in Arabia? It is very salty. Swimmers cannot sink in it! Fish cannot live in the Dead Sea. It is a strange sea. In most parts of the sea, there are a lot of fishes and plants. Some live near the top of the sea. Others live deep down. No sunlight can reach the depth of the sea. So it is completely dark. Strange fishes live there. Some are blind. Some have their own lights. Some have great jaws. With their great jaws, they swallow fish larger than themselves. The sea can be very cold. Deep sea divers know this well. At the top of the water may be warm. Then as the divers go down, the sea becomes colder and colder.   Many scientists are now making a study of animal and plant life in the sea. They hope to find new resources for mankind. The Dead Sea is lifeless because   _  .
the water in it is too cold the water in it is too salty for anything to grow the water in it never flows no sunlight can reach the bottom of the lake