Task: Question Answering
Input (English): Question: The mechanism of a homogeneous chemical reaction: 
 Options:  <1> It may include reaction intermediates that are not any of the reactants or any of the products. <2> It is completely defined by the chemical reaction as long as it reflects the correct stoichiometry of the reaction. <3> It is only defined for complex reactions in which the reactants go through many stages before becoming products. <4> It is totally independent of the law of reaction speed. <5> It does not depend on the temperature and is unique for the reaction between certain reagents.
Output (English): 1