Task: Question Answering
Input (English): Question: The main function of chemokines is: 
 Options:  <1> Regulate lymphocyte traffic. <2> Stimulate cell proliferation in response to chemical agents. <3> Amplify the production of antiviral cytokines. <4> Regulate the selection in the thymus. <5> Antagonize some cytokines.
Output (English): 1