A common feature of textbooks that enhance online learning is ______.

Practice quizzes are a common feature of textbooks that enhance online learning because they provide students with an opportunity to engage actively with the material and test their understanding in a structured way. These quizzes help reinforce learning by allowing students to apply what they have studied, identify areas where they may be struggling, and ultimately improve retention of the concepts. Additionally, immediate feedback from these quizzes can guide students in their learning process, helping them focus on topics that require more attention.

While other options like interactive video content, access to forums, and live assistance also serve valuable functions in an online learning environment, practice quizzes specifically target reinforcement of knowledge and self-assessment, making them a particularly effective tool in the context of learning from textbooks.