我自己的翻译是:pong是一个经典游戏,许多现有的计算机娱乐都来源于它, 这样来说,FLIP IT的句子才对呀,为什么是第三个句子对? Uncertain: Pong is a classic game from which have/has descended many current computer pastimes. Flip it!  ong is a classic game from which many current computer pastimes HAVE descended. Right:  ong is a classic game from which HAVE descended many current computer pastimes.