Which materials are used for items 1-3 in BD?

The correct answer indicates that both the model and the picture are integral materials used for items 1-3 in the Block Design (BD) subtest of the WISC-V. This subtest is designed to assess a child's visual-spatial skills and their ability to analyze and synthesize visual information.

Using a model provides a three-dimensional representation that helps the child understand the spatial relationships they need to replicate. The accompanying picture serves as a two-dimensional visual guide that further clarifies what the completed design should look like. Together, these materials facilitate a comprehensive understanding of what is being asked of the child, allowing them to effectively demonstrate their abilities in this area of cognitive processing.

In contrast, relying solely on a picture without the model might limit a child's understanding of depth and structure, while using only a model without any visual representation could make it challenging for the child to conceptualize the exact design. Therefore, utilizing both materials enriches the task, ensuring that children can leverage all available cues to perform their best. No materials would not allow for the task to be completed at all, which is also not effective in measuring the cognitive skills intended to be assessed in the Block Design subtest.