Task: Question Answering
Input (English): Question: Azidothymidine (AZT) used against the human immunodeficiency virus: 
 Options:  <1> It binds to the cellular RNA polymerase and blocks transcription. <2> It binds to the early promoter of the virus and prevents its recognition by RNA polymerase. <3> Antagonizes the phosphorylation of nucleosides, thus inhibiting the synthesis of viral DNA. <4> Blocks the transport of thymidine to the cellular interior. <5> Inhibits transcriptase
Output (English): 5