题目

Governments around the world are pushing for an end to plastic straws (吸管 ) and bags. More and more businesses are turning to paper products as a choice. Paper is considered by many to be better than plastic. However, it, too, is harmful to the environment. Firstly, paper bags and straws are made from trees. Trees, as you know, can reduce (减少 ) carbon dioxide ( 二氧化碳 ) levels in the atmosphere. They can slow down climate (气候 ) change. An increase in the use of paper bags can cause more acts of cutting down trees. Secondly, products made from paper require more energy and 如图，已知CD是△ABC中AB边上的高，以CD为直径的⊙O分别交CA，CB于点E，F，点G是AD的中点．求证：GE是⊙O的切线．