Given the task definition and input, reply with output. In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.

Robin: Holy escape hatch !
Batman: Yes , Robin , most refrigeration systems as large as this _ one _ in the Bruce Wayne Ice Arena have emergency exits .
Robin: It 's lucky you remembered the one behind that vaporizing tube when you did .
Batman: You 're seldom wrong , old chum , but a split second is longer than you realize .
Robin: Long enough for Mr. Freeze , so that he split too I see .
Batman: No doubt taking Professor Isaacson with him and his frosty convederates and Emma Strunk .
Robin: You mean Glacia Glaze ?
Batman: No Robin , Emma Strunk .
Robin: No , you mean Glacia Glaze !
Batman: No , Emma Strunk ! Glacia Glaze is far too charming a pseudonym for one of her chilling corruption .
systems