Which of the following statements about functional groups is true?

Functional groups are specific groups of atoms within a molecule that are responsible for the characteristic chemical reactions of that molecule. They essentially determine how an organic compound will react with other substances. Each functional group has a unique structure and set of properties, leading to predictable behavior in chemical reactions. This means that the presence and type of functional groups can guide chemists in predicting how different organic molecules will interact, making this statement undeniably true.

In contrast, the other statements are inaccurate as functional groups are not exclusive to inorganic compounds, nor do they represent the entire molecular structure; they are only a part of it. Additionally, functional groups actively participate in chemical reactions, which directly contradicts the notion that they cannot undergo such processes. Thus, the correct understanding of functional groups is central to organic chemistry and their role in determining reactivity is fundamental.