A、An environment-friendly battery. B、An energy-saving mobile phone. C、A plant-powered mobile phone charger. D、A device to help p

(5)Three university students in Santiago, Chile, have developed a plant-powered device to charge their mobile phones.
     (6)The three engineering students got the idea for the device while sitting in their school’s courtyard. Their invention is a small biological circuit they call E-Kaia.(7)It captures the energy which plants produce during photosynthesis—a process of converting sunlight into energy.
    A plant uses only a small part of the energy produced by that process. The rest goes into the soil. E-Kaia collects that energy. The device plugs into the ground and then into a mobile phone.
    The E-Kaia solved two problems for the engineering students. They needed an idea for a class project. They also needed an outlet to plug in their phones.
    One of the student inventors, Camila Rupcich, says the device changes the energy released from the plant into low-level power to charge phones.
    The E-Kaia is able to fully recharge a mobile phone in less than two hours.
Questions 5 to 7 are based on the news report you have just heard.
5. What did the three university students invent?
6. When did they get the idea for the invention?
7. What does the speaker say about the invention?