Final answer:
The primary reason to use pre-manufactured cap shingles is for faster installation, facilitating a quick and efficient roofing process.
Step-by-step explanation:
The primary reason to use a pre-manufactured cap shingle is c. Faster installation. Cap shingles are designed to fit perfectly at the ridge and hip lines of a roof, which eliminates the need for cutting and shaping on-site. This standardized production ensures a quick and efficient installation process, saving time and labor costs. While they may also offer improved aesthetics and durability, their primary advantage and purpose is to streamline the roofing process.