The center of gravity of projecting masonry or molded cornices must lie within the middle ____ of the supporting wall:

The center of gravity of projecting masonry or molded cornices must lie within the middle third of the supporting wall to ensure stability and prevent excessive stress on the wall structure. This rule is established to maintain balance and proper distribution of weight, which is critical when dealing with structures that extend outward. When the center of gravity lies within this zone, the forces acting on the cornice are well aligned with the supporting wall, minimizing potential tipping or pulling effects that could lead to failure.

Having the center of gravity in the middle third provides an additional safety margin, allowing for some degree of movement or load fluctuations without compromising structural integrity. This practice is crucial in building design and inspection, as it enhances the overall safety and longevity of the structure.

The other options indicate different proportions that would not provide the same level of stability. If the center of gravity were placed in the middle quarter or other fractions, there could be higher risks of the cornice detaching under load or environmental forces.