Marcenia doubled back toward third. When the catcher threw the ball back to the third baseman, Marcenia turned and bolted toward home plate. As the ball sailed above her head, Marcenia pumped her arms and knees harder.
Usually there's one person on the first base, one person on the second base and one person on the third base: the first baseman, the second baseman, the third baseman.
通常一垒一个人,二垒一个人, 三垒一个人:一垒手, 二垒手,三垒手。
英语百科
Third baseman
A third baseman, abbreviated 3B, is the player in baseball whose responsibility is to defend the area nearest to third base — the third of four bases a baserunner must touch in succession to score a run. In the scoring system used to record defensive plays, the third baseman is assigned the number '5'.