关于why toucan（巨嘴鸟）evolved a bill。
1. weapons against predators;
2. color and shape to hide from predators;
3. get rid of excess body heat;
1. The bill cannot function as a weapon. It’s made of hollow bones filled with air, so it’s thin and lightweight or else toucans can’t fly. If it’s used as a weapon, it will be easily damaged in activities like jabbing.
2. Toucans have to call out to each other in order to use the color and shape to blend into surrounding areas. If they do this, they will draw the attention from the predators.
3. Healthy toucans don’t use their bills. They need bill to get rid of heat in the daytime, but at night when the temperature is lower, they always hide their bills to retain body heat.
2. 宗教变化(religious change);
2. 宗教一直在overlapped and mixed, 不但没有decline, 而是更加flourish;
1. 教育类：Which is better for children's education: 9-month study and 3-month break or 3-month study and 1-month break?
2. 媒体类：Do you agree or disagree with the following statement? For any business to be successful, it must spend a lot of money on advertising.
3. 社会类：Do you agree or disagree with the following statement? It is as important for older people to study and learn new things as it is for younger people.