把陈述句换成把字句。

①孙青在操场上找到了丢失的钢笔。

②一阵清脆的铃声惊醒了睡梦中的小芳。

—Your T-shirt is nice. It must be expensive.

—Not at all. I only spend $10 　　　 it.

— What a touching love story!  The main character Song Joongki in the Korean drama Descendants of the sun(太阳的后裔）acts very well.

— Really? When _______ it?

My interest      football began when I was 9 years old．    

如图是一个以点A为对称中心的中心对称图形，若∠C =90°，∠B = 30°，AC = 1，则BB′的长为（  ）