足球运动员必须把球准确地踢过中线。

The soccer player must kick the ball precisely over the ___centreline.

设计师沿着中心线对折纸张以确保两边完全对称。

The designer folded the paper along the ___centerline to ensure perfect symmetry on both sides.

球员必须把球带回中线才能重新开球。

Players must bring the ball back to the ___centreline to restart the game.