A：和平稳定的历史
B：诸侯争霸的历史
C：经济发展的历史
D：百家争鸣的历史
Tom is in Class 1 and I am in Class 2. ______ are not in the same class.
- These problems are too hard to . Will you give me some advice?
- There are many ways. The most important is to have a careful plan.
△ABC与△A′B′C′是位似图形，且△ABC与△A′B′C′的位似比是1：2，已知△ABC的面积是2，则△A′B′C′的面积是（ ）
