【正文】
s made of gores and panels as its body, with a parachute valve on its top and a skirt at its bottom. The basket, where the passengers and pilots stand and the propane cylinder is set, is connected to the envelope by several ropes. The picture illustrates the working principle of a hot balloon. By contrast, the Aomori Hakodate Tunnel in Japan was a domestic one. It was built to connect the cities of Hokkaido and Honshu. Instead of a mountain, this tunnel was built beneath water area, which is km in width and 132 metres in depth. Moreover, the construction is a bination of three straight tubes with a total length of km to fit the shape of the water Reaching the depth of 240 metres from the water surface, the bottom of the tunnel is even deeper than the water to avoid the very hard stone layer 0f quartzite around. This construction takes workers nearly 25 years to plete it.八 The two pictures show the construction structures of two tunnels. They are different in many aspects. When we are short of water in the forest or field, this simple set may be the easiest way for us to get rid of thirst七 The materials needed for this set are all easy to get. Firstly, prepare two glasses, one of which is much larger than the other. Secondly, find some green plants as the resource of water. Thirdly, set the green plants and put the small glass into the larger glass, then cover the opening of the larger glass with 171。 Summarize the information by selecting and reporting the main features. The diagram below shows how to obtain water outdoors. In conclusion, plants, humans and animals provide services for each other. Humans and animals need the oxygen