Which statement about the installation of flexible lines is true?

The statement that flexible lines require a slack of 5 to 8 percent is accurate because flexible lines, especially those used in hydraulic or fuel systems, need some degree of slack to accommodate normal expansion and contraction during operation. This slack helps prevent undue stress on the lines that could lead to kinking or failure over time. Installing them too tightly could restrict their movement and lead to damage, while having no slack at all can create tension that is detrimental to their longevity and performance. Therefore, the recommended slack allows for movement and flexibility, ensuring that the lines function effectively without compromising their integrity.