①秦始皇统一文字 ②宦官蔡伦改进造纸技术 ③汉武帝在长安举办太学 ④隋炀帝时开凿贯穿南北的大运河
A:①②
B:①③
C:①②③
D:①②③④
Good books are like wise friends, because _____ support you to walk forward and help you understand the world.
计算:222-5=____ .