Which of the following is NOT a characteristic of effective instructional materials?

Effective instructional materials are designed to enhance the learning experience and ensure that students can understand and engage with the content being taught. One of their primary characteristics is to support student engagement, making the learning process interactive and compelling. Additionally, such materials facilitate the achievement of learning objectives, directly aligning with what students are expected to learn and demonstrating clear pathways to those goals.

Moreover, effective instructional materials are adaptable for various learning styles. This means that they can be modified or presented in different ways to cater to the diverse preferences of learners, ensuring that all students have the opportunity to grasp the concepts being taught.

In contrast, the characteristic of being confusing and hard to understand directly undermines the purpose of instructional materials, which is to promote clarity and comprehension. Therefore, this aspect stands out as the one that does not align with the defining traits of effective instructional resources.