An Australian inventor has designed and built an environmentally friendly ferry  that uses solar and wind power to transport people around Sydney Harbor. Robert Dane and his Solar Sailor were given the top prize at the Australian Design Awards recently.      The Solar Sailor has been in use for six months. It uses four sources of energy for its power -- solar, wind, battery power with stored solar energy and a fuel generator  in store all controlled by computers. The ferry can travel up to 7.5 knots on just wind and solar power. It's solar wings and fiberglass solar panels   which not only take in sunlight and store it in batteries, but also act as sails.       "We angle  our solar panels to the sun in two planes , which increases the amount of energy we get from the sun by 40 percent," Dane says. "And also we can use that same structure to do another job, which is also the sail, and so these wing sails actually push the ferry forward just like a soft sail does."       Computers check the sun and wind and angle the solar wings to take in the most sunlight. If there isn't much wind or it is a cloudy day, energy stored in the batteries runs the electric motor for up to five hours. "If the batteries are too low, then the computer turns the generator on so the boat is always able to meet a commercial schedule, or get from point A to point B no matter what," Dan explains.      Dane got his idea for the Solar Sailor from a book on insects. He was amazed how insects use their wings to collect solar energy to warm themselves.       "When I read that, I realized there was a good example in nature for what we were going to do, which was to use a solar wing to collect solar energy and also to sail," he says. What is the purpose of writing this article?
To praise the designer Robert Dane. To make an advertisement. To tell us to learn from nature. To introduce a new invention.
Question: An Australian inventor has designed and built an environmentally friendly ferry  that uses solar and wind power to transport people around Sydney Harbor. Robert Dane and his Solar Sailor were given the top prize at the Australian Design Awards recently.      The Solar Sailor has been in use for six months. It uses four sources of energy for its power -- solar, wind, battery power with stored solar energy and a fuel generator  in store all controlled by computers. The ferry can travel up to 7.5 knots on just wind and solar power. It's solar wings and fiberglass solar panels   which not only take in sunlight and store it in batteries, but also act as sails.       "We angle  our solar panels to the sun in two planes , which increases the amount of energy we get from the sun by 40 percent," Dane says. "And also we can use that same structure to do another job, which is also the sail, and so these wing sails actually push the ferry forward just like a soft sail does."       Computers check the sun and wind and angle the solar wings to take in the most sunlight. If there isn't much wind or it is a cloudy day, energy stored in the batteries runs the electric motor for up to five hours. "If the batteries are too low, then the computer turns the generator on so the boat is always able to meet a commercial schedule, or get from point A to point B no matter what," Dan explains.      Dane got his idea for the Solar Sailor from a book on insects. He was amazed how insects use their wings to collect solar energy to warm themselves.       "When I read that, I realized there was a good example in nature for what we were going to do, which was to use a solar wing to collect solar energy and also to sail," he says. What is the purpose of writing this article?
A. To praise the designer Robert Dane.
B. To make an advertisement.
C. To tell us to learn from nature.
D. To introduce a new invention.
Answer: