Answer:
B. The level of formality that best fits the topic and the audience.
Step-by-step explanation:
The speaker of a speech should acknowledge his audience and establish which language is most appropriate for that audience. It would be very inappropriate if a speaker used informal language in an academic-level speech at a university, similarly it would be equally inappropriate to use formal language full of technical terms for kindergarten children. From this we can state that an important style decision a speaker makes when writing a speech is to choose the level of formality that best fits the topic and audience.