What factor greatly impacts a transitioning-level English language learner's comprehension of a content-area textbook chapter?

A transitioning-level English language learner often encounters challenges when engaging with content-area textbooks, and one significant factor that influences their comprehension is the amount of prior knowledge about the topic. When students have background knowledge related to the subject matter, it facilitates the integration of new information with what they already know, leading to improved understanding. This existing knowledge serves as a mental framework that helps learners make connections, infer meanings, and retain new concepts presented in the text.

The other factors mentioned can also affect comprehension, but they do not have the same foundational impact. For instance, complexity of vocabulary can hinder understanding, but if a learner has some prior knowledge of the subject, they may be able to deduce meanings from context or use that knowledge to work through difficult terminology. Similarly, while illustrations can aid comprehension by providing visual context, they are most effective when coupled with relevant background knowledge. Lastly, the length of the text can sometimes be daunting, but it is the understanding of the content itself that truly drives comprehension; thus, prior knowledge remains a crucial factor in overcoming these challenges for language learners.