CMUs are often used in all these except:

CMUs, or concrete masonry units, are widely utilized in various construction applications due to their strength, durability, and versatility. They are particularly suitable for foundation walls, retaining walls, and basement walls because they provide excellent structural support and resistance to environmental factors such as moisture.

In foundation walls, CMUs help support the weight of the structure above while providing a sturdy barrier against water infiltration. For retaining walls, they are ideal due to their ability to withstand lateral pressure from the soil they are holding back. In basement walls, CMUs create a solid and reliable framework that can withstand the below-grade conditions, providing both structural integrity and moisture resistance.

However, CMUs are not typically used in rafter construction. Rafters are generally made from wood or engineered wood products, as these materials are lighter and more suited for forming the pitched roof structures that rafters create. The requirement for lighter materials in roofing applications and the need for material adaptability makes wood a preferred choice rather than concrete masonry units. Thus, CMUs do not find application in rafter construction, making that the correct choice in this context.