题目

My mother ________ (be) angry with me, but I couldn't shut my mouth before I shouted at her! 答案：wouldn't have been 句意：我母亲本来不会对我生气的，但我没有管住自己的嘴，对她大吼大叫了！wouldn't have done “本来不会做某事”。如图（九），一个正方体的棱长为2cm，一只蚂蚁欲从A点处沿正方体侧面到B点处吃食物，那么它需要爬行的最短路径的长是         .