In a diamond formation, what must the center line(s) in the block be?

In a diamond formation, the center line(s) in the block must be the longest lines. This is essential for maintaining the visual and structural integrity of the formation. The longest center line helps to create a balanced and symmetrical appearance, which is crucial in synchronized skating for both aesthetic appeal and technical precision.

When all lines radiate from a single point to maintain a diamond shape, the longest center line establishes a focal point that guides the formation's overall geometry. Having a longer center line also helps to define the space and alignment of the skaters, ensuring that the formation holds its shape as they move.

The other options do not serve this structural purpose: shorter lines would disrupt the balance, equal lengths would not support the intended shape, and varying lengths would cause misalignment within the formation, making it chaotic rather than harmonious. Thus, the emphasis on the longest center line in maintaining the diamond formation is critical for performance quality.