Concept:A good language textbook must be visually appealing and easy to understand to help students learn effectively.Explanation:The main purpose of a language textbook is to give clear and interesting reading material. Attractive fonts, colourful illustrations, and simple, learner-friendly texts make the book engaging. They help students read with ease and understand better. While interesting stories are useful, they alone do not make a textbook good. Grammar exercises and extracts from foreign literature are not the most important features. For upper primary students, the textbook should focus on presentation and readability. Therefore, the best choice is the one that includes attractive design and easy-to-follow content.Answer:D. attractive fonts, illustrations and learner-friendly texts