1. **Problem Statement:** We have a stack of 7 identical cubes arranged in a stepped form. We want to find the minimum number of additional cubes needed to complete this stack into a rectangular prism. 2. **Understanding the shape:** A rectangular prism is a box-shaped solid with length, width, and height all rectangular and filled completely with cubes. 3. **Determine dimensions of the rectangular prism:** - The base layer has 3 cubes arranged in a row (length = 3). - The middle layer has 3 cubes offset inward, so width = 2 (since the middle layer is narrower). - The top layer has 1 cube, so height = 3 (3 layers total). Thus, the rectangular prism dimensions are $3 \times 2 \times 3$. 4. **Calculate total cubes in the rectangular prism:** $$3 \times 2 \times 3 = 18$$ 5. **Calculate how many cubes are missing:** - Current cubes = 7 - Total cubes needed = 18 - Additional cubes needed = $18 - 7 = 11$ 6. **Answer:** The minimum number of cubes needed to complete the stack into a rectangular prism is **11**. Therefore, the correct choice is C) 11.