他在业余时间做自由摄影师，作为副业来增加收入。

He works as a freelance photographer in his spare time, which is his ___sideline to earn extra money.

裁判判定球碰到了边线，比赛继续。

The referee ruled the ball hit the ___sideline, so the game continued.

脚踝受伤使他无法参加接下来的比赛。

An ankle injury ___sidelined him for the next few games.