下列字体演变的先后顺序是：（）
①甲骨文
②隶书
③小篆
④楷书
A.①②③④
B.②③④①
C.①③②④
D.④③②①
参考答案：C
在直角三角形ABC中，∠C=90°，且c+a=9，c-a=4，则b=______．
We were all surprised when he made it clear that he ______ office soon.
A．leaves
B．left
C．would leave
D．had left
