9．The Cabbage White butterfly （菜粉蝶） has a natural range across Europe，Asia，and North Africa．To many farmers，the butterflies are regarded as a pest（害蟲 ）； to others，they are pretty to look at．Researchers are looking into new ways to make efficient photovoltaic（光電的） energy and for this they have been inspired by the v-shape posture of the Cabbage White butterfly．Photovoltaic energy is the science behind solar power，where light is turned into electricity．
To improve the collection of sunlight，a research group have been inspired by the resting posture of the Cabbage White butterfly．The butterfly keeps a"v"shape in order to heat up its flight muscles before taking off．By creating solar panels（板）in this shape，scientists think that the quantity of power that a solar panel can use can be increased by around 50 percent．
The crucial part is the weight of solar panels．For this the researchers developed a kind of material that is lightweight．The Cabbage White butterfly is different to many other butterflies because it is using the v-formation．On cloudy days common butterflies need to wait to receive enough sunlight in order to fly．However，by owning the v-shape posture the Cabbage White butterfly is able to receive more energy more quickly than other butterflies．In addition，the butterfly can flash back sunlight from its wings，which allows its flight muscles to be warmed up to the best temperature．
The new research was done at the University of Exeter's Environment and Sustainability Institute （ESI）．Dis cussing the findings，lead researcher Professor Tapas Mallick stated："This engineering is not new．However，this research，which shows ways to develop low-cost solar power，has not been done before．"
19．What does the underlined word"crucial"in Paragraph 3 mean？A
A．Important．B．Easy．C．Useful．D．New．
20．Which is the main benefit of the butterfly's v-shape wings？D
A．They always keep the butterfly warm．
B．They can help the butterfly fly much higher．
C．They can help the butterfly avoid danger．
D．They can help the butterfly get more sunlight．
21．Common butterflies need to wait on cloudy days becauseB．
A．they wait to get enough wind
B．they lack enough energy to fly
C．their muscles need to move first
D．they wait to turn wings to a V shape
22．What can be a suitable title for the text？A
A．Butterflies inspire new types of solar power
B．How to develop the new kind of solar power
C．Butterflies help the scientists do research
D．A new achievement about solar power．
