Paul Rusesabagina might mean that words have the power to make people act or react in a certain situations. Let´s take an example from his text, he asked the question "What had caused this to happen? Very simple: words" He is referring to a "cool" guy who ends up being a militar carrying guns so Paul blames his parents because he thinks that he might have been told "over and over again" how stupid he was, how he never would be attractive or physically fit. This was used to enforce the power of the elite. So this might be considered a clear case in which due to words a person might decide his future. <span />
The correct answer is tone. Imagery is using vivid description while style is the personal type of narration like what words they use or grammatical constructions. Theme is the underlying idea while the voice is seen through the tone, whether it's dark and broody or joyful or anything similar.