1. He had to extemporize a speech when his prepared notes were lost.
当他准备的笔记丢失后，他不得不即兴演讲。

2. The actor had to extemporize in order to cover up his forgotten lines.
为了掩饰他忘记的台词，演员不得不即兴演出。

3. As a jazz musician, he is skilled at extemporizing solos.
作为一名爵士乐手，他擅长即兴创作独奏。