Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: It has been proven that amphetamines have reinforcing effects because: 
 Options:  <1> They are GABAergic agonists. <2> They are dopaminergic antagonists. <3> They are serotonergic antagonists. <4> They are dopaminergic agonists. <5> They are serotonergic agonists.
