原子弹和核电都是利用链式反应，两者的本质区别是：原子弹爆炸时发生的链式反应是 ____，核反应堆中发生的链式反应是____．

阅读理解

    My name is Eve Smith. This is a photo of my family. There are five people in the photo. Look! The old woman is my grandma. She is seventy years old. The woman in red is my mother. She is a doctor in a hospita l. The man in a black coat is my father. He is a teacher in a middle school. This tall man is my uncle. He is my mother's brother. He is next to my mother. I'm in yellow.

   We live in this house. Look here, please! In front of our house, there is a small garden. It’s very nice. There are many beautiful flowers and some small trees in the gard e n.

产业转移可以大力促进区域的产业结构调整。有①②③三个地区，其产业都是在产业转移的基础上逐步发展起来的，下图为目前这三个地区的产业投入比重。回答下题。

产业转移的正确顺序是（   ）

A____可以得到B。