Which of the following is a factor that can disrupt reading fluency?

The correct answer is that a lack of familiarity with vocabulary can significantly disrupt reading fluency. When readers encounter words that they do not recognize or understand, it slows down their reading process. They may pause frequently to decode unfamiliar terms, which interrupts the flow of reading and affects overall comprehension. Vocabulary knowledge is essential for fluency because fluent readers are able to recognize words automatically, allowing them to focus more on understanding the text rather than struggling to read the words themselves.

In contrast, excessive background knowledge, high proficiency in reading, and frequent exposure to complex texts generally support and enhance reading fluency rather than disrupt it. A reader who is well-versed in the subject matter will likely process information more easily and quickly, while high proficiency signifies a developed skill set that includes fluency. Frequent exposure to complex texts can challenge and improve a reader's skills, encouraging growth rather than hindrance in their reading abilities.