|问题5：What did the three university students invent?|
答案：A plant-powered mobile phone charger(充电器).
（文章第一句）： Three university students in Santiago, Chile, have
deveoped a plant-powered device to charge their mobile phones.
提示： 注意题干与文章相关句中近义词的替换： invent -- develop
问题6：When did they get the idea for the invention?
答案：While sitting in their school's courtyard.
The three engineering students got the idea for the device while sitting in their school's courtyard.
问题7： What does the speaker say about the invention?
答案： It collects the energy released by plants.
It captures the energy which plants produce during photosynthesis -- a
process of converting sunlight into energy.