A：血液中O2浓度的变化
B：血糖浓度的变化
C：环境中温度的变化
D：感染人体的流感病毒
下列实验操作中，正确的是（ ）
《槐乡五月》开头连用了三个比喻句，找出这句话。抄下来，仔细品味。
In the second lesson, the teacher still____him to draw an egg, but he____the egg on a plate. Little Leo____unhappy and asked, "____do we draw eggs all the time?" "Look ____. It's an egg again, but it looks____." said the teacher.
下列反应属于置换反应的是（ ）
