Task: Question Answering
Input (English): Question: Choose among the following phrases the one that most appropriately defines a concerted reaction: 
 Options:  <1> Reaction in a single stage in which all the links that are formed and break do so at the same time. <2> Reaction in several stages in which all the links that are formed and break do so at the same time in the slowest stage. <3> Reaction in which the speed of all stages is identical. <4> It is an equilibrium reaction in which K = 1. <5> Reaction in several stages in which all the links that are formed and break do so at the same time in the fastest stage.
Output (English): 1