主持人做了简短的介绍后，演讲者开始发言。

The host gave a short ___introduction before the speaker started.

请先阅读引言部分，它概括了这本书的主要内容。

Please read the ___introduction first, as it summarizes the main content of the book.

新软件的引入大大提高了我们的工作效率。

The ___introduction of new software significantly improved our work efficiency.

这本手册包含了对摄影技巧的简单介绍。

This manual includes a basic ___introduction to photography techniques.