To save time, many Americans buy foods which can be quickly made ready for the table. On holidays, families enjoy delicious meals. For example, on Thanksgiving Day, the fourth Thursday in November, family members get together for a turkey dinner with pumpkin pie(南瓜派).

    People can easily find fast food chains(连锁店),such as McDonalds' and KFC, in most of the big cities in the world.

    These years, many people have taken more and more care of their health while eating. They come to know eating too much meat will make them overweight. Many of them are also worried about food addictives(添加剂). Some of them may be harmful to the body.

在化学实验技能考试中，有一题目是鉴别氢氧化钙溶液和氢氧化钠溶液，某同学进行了如图所示的实验．

枯叶蝶在进化过程中逐渐形成了体色随环境变化的特点；飞行过程中身体呈鲜艳的黄色，便于吸引异性，降落后的体态和体色像一片枯叶，下列叙述错误的是（  ）