listen to the material carefully,although it is difficult and sometime you can't write down the correct answer.As long as you have tried,whatever you write down will be the harvest of yours.You should believe that only by accumulating little by little could you learn English welll.so come on.
This prototype solar reactor uses a metal oxide called ceria, heated up in the concentrated glare of the Sun, and __________________________________, which could be used to power hydrogen fuel cells in cars for example. The prototype is grossly inefficient, converting less than 1% of the Sun's energy into fuel energy, but its makers are confident that they can ramp up that efficiency to near 20%, using better insulation and perfecting the lens through which the Sun pours into the machine.