Answer: A) Complexity.
Explanation: complexity is the state of having many parts and being difficult to understand or find an answer to, its antonym is simplicity which means the quality or condition of being easy to understand or do. From the given options, the one that correctly completes the sentence, is the corresponding to option A: complexity, so he answer would be "A topic with a great deal of complexity needs to be simplified for your audience" (because of the difficulty of the topic, it needs to be simplified).
