Which connective tissues are arranged in tight, parallel lines and resist tensile stresses in one direction only?

The correct answer describes connective tissues that are specifically designed to withstand tensile stresses, demonstrating strength and resistance in a singular direction. These tissues are fundamentally composed of densely packed collagen fibers that are aligned parallel to each other. This arrangement allows them to effectively handle pulling forces without easily stretching or deforming.

In the context of the focus on tensile strength in one direction, tendons are the prime example of this characteristic. Tendons connect muscles to bones and are structured in such a way that they can endure the tension generated when muscles contract. Their parallel fiber arrangement ensures maximal resilience to directional stress, which is critical for their function in facilitating movement.

While cartilage and ligaments are also forms of connective tissue, they serve different functions and are structured differently, with cartilage providing cushioning and support and ligaments connecting bone to bone, often allowing some degree of movement. Fibers, on the other hand, is not a specific type of complete connective tissue like the others listed, and doesn't denote any particular structural properties. Hence, tendons are the most accurate response to the question about connective tissues that function effectively under tensile stress in one direction only.