The first grade corresponds to the row player, me in this case, and the second grade in each box corresponds to the column player, my pair in this case.

单元格内第一个成绩是我的成绩,每个单元格第二个成绩是,我对手的成绩

耶鲁公开课 - 博弈论课程节选

That's because you have to satisfy this base pair matching in order to have hydrogen bonding in each of the struts of the ladder in order to form a stable structure.

NA双链要满足互补配对原则,以使碱基对之间,形成氢键,从而形成稳定的双链结构

耶鲁公开课 - 生物医学工程探索课程节选