质量为m=4kg的小物块静止于粗糙水平地面上．现用F=12N的水平恒力拉动小物块，经过时间t=2s，小物块运动了x₀=4m的距离，取g=10m/s²．求：

中学生情感丰富，情绪复杂多变。遇到事情容易头脑发热、意气用事，极可能造成无法弥补的恶果。这警示我们（    ）

某化学课外小组用海带为原料制取少量碘水，现在用四氯化碳在碘水中萃取碘单质，并用分液漏斗分离两种溶液．

根据阅读内容选出正确选项。 

    This is a picture of my uncle. He likes math. He works in a bank. He helps the bank use their money well. He likes working with numbers. He goes to work by car, but sometimes he walks. My aunt is an engineer. She likes drawing pictures. She works in a big company. She designs computers. She goes to work by bus.  

我国计划生育要求晚婚提倡比法定结婚年龄晚____ 年结婚。