What is the purpose of "Earth Hour"? 

A)  to save as much energy as possible in a day 
B)  to publicize and market new energy devices 
C)  to increase the profile of politicians and celebrities 
D)  to create awareness and public involvement regarding energy issues affecting the world

Earth Hour is an annual event that started in 2007 and is meant to raise awareness about energy consumption and climate change. The purpose is to encourage people and businesses to turn off non-essential lights and appliances for one hour. The event has since grown into a global movement with participation from individuals, businesses, and governments around the world. Therefore, the best choice is D - to create awareness and public involvement regarding energy issues affecting the world.