Firstly, let's see what the book is about.首先, 让我们看看这本书的内容。

Noise affects us in two ways. Firstly, it can damage hearing.噪音影响我们的方式有两种。第一, 它可以损害人的听力。

The programme is now seven years behind schedule as a result, firstly of increased costs, then of technical problems.该计划的实施比原计划晚了七年, 一是因为成本增加, 二是由于技术问题。