The golden rule in tennis is to keep your eye on the ball.

打好网球的重要原则是眼要紧盯着球。

《牛津词典》

Experienced players use this rule without thinking, and do worse if instead they try to work out where the ball is going to land and run there.

有经验的球员自觉地利用了这一规律，如果他们尝试计算出球的着地点并以此为奔跑方向，那么，他一定不是好球手。

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Robots that cause damage to the field or the ball during normal game play can be disqualified (see Rule 2.8).

机器人在正常比赛中损坏比赛场地或足球的，取消其比赛资格。(见2.8)。

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Reggie Greenwood, the conference coordinator of officials, said afterward that because the play happened during a dead ball, by rule the foul was a technical.

WSJ: Charlotte stuns Richmond at A-10 tourney 68-63

Then the Scarlets needed the help of the video referee to rule the ball had not been grounded in a melee of bodies on the line.

BBC: Scarlets 43-34 Perpignan

Myler narrowly missed the extras but Castres responded immediately only for the video referee to rule the ball had not been grounded as they attempted to drive over.

BBC: Castres 12-23 Northampton