Answer: C. the age range of the readers.
The most likely answer to this question is option C. The age range of the readers is important when trying to determine what is a suitable topic for an audience. Although the purpose and the topic are linked, they do not necessarily depend on each other. Moreover, the form that the author wants to use does not depend on the topic. The size of the audience is similarly irrelevant. However, the age range of the readers is an important factor to take into account. Young readers might not be prepared to deal with topics that are suitable to an older audience.
