Final answer:
The percentage of properties that must be considered as 'physical blight' before required to be repaired is not specified by a standard threshold and can vary by local legislation. It is a complex issue part of urban renewal efforts and is subject to specific local ordinances and redevelopment plans.
Step-by-step explanation:
The question of what percentage of properties within a community must be considered as 'physical blight' before they are required to be repaired is not universally defined and can vary by jurisdiction. However, none of the percentages provided in the options (10, 13, 16) is a standard threshold. Instead, the determination of 'blight' and the consequent urban renewal strategies depend on specific local ordinances and redevelopment plans. While the idea of urban renewal was to address the visual and structural decay of inner cities, it often involved significant changes to the community and sometimes unexpected consequences.
Actions to remediate urban blight are usually driven by local legislative bodies in conjunction with redevelopment agencies. They assess the extent of decay and make decisions on a case-by-case basis. It involves not just repairing buildings but a comprehensive approach that may include demolishing buildings, creating new investments, and relocating displaced residents to newer, cleaner, and safer housing.