15、On April 9，2010，a solar-powered plane successfully made its first flight．It flew at a speed of 70 km/h at a height of 1，200 meters in the sky above Switzerland for 87 minutes．It is the first solar-powered plane in the world．A group of engineers，led by Bertrand Piccard，a well-known pilot，made this plane．

The solar-powered plane is different from the planes that we usually see．The' plane has a thin body with two very big wings full of solar cells．It uses sunlight as its energy, but it was not easy to make such a plane．First of all，Bertrand Piccard and his group members had to find out how to get energy from the sun．They used 12，000 solar cells to catch the sunlight．Then they had to find a good way to store it．They used special batteries to store the energy．What's more，the plane should be light enough so that it would not use too much power．It should also be strong enough to hold its body to fly in the sky．They used the strongest and lightest materials" to build the plane．It weighed 1，600 kg and only needed the power of a small car．

After this successful flight，Bertrand Piccard said，"The airplane has landed but we have not yet landed．"Their next step is to have a non-stop flight around the world by 2013．Before they can do that，they will have to work out how the plane can store enough energy during the day and keep flying at night．Also，the team will have to watch the weather closely to make sure the plane can fly．

1．How long did the solar-powered plane fly in the sky on April 9，2010?

A．9 minutes．                                            B．70 minutes．

C．87 minutes．                                          D．1，200 minutes．

2．Where is the energy of the solar-powered plane from?

A．The sun．                  B．Air．              C．The moon．      D．Wind．

3．The first solar-powered plane weighed _______

A．1，200 kg                                            B．1，600 kg

C．12，000 kg                                                 D．16，000 kg

4．When can the solar-powered plane take a non-stop flight around the world?

A．When it is light enough to fly in the sky．

B．When it is strong enough to hold its body to fly in the sky．

C．When it looks different from the planes that we usually see．

D．When it can store enough energy during the day and keep flying at night．