Given the task definition and input, reply with output. In this task, you are given a sentence in the Spanish language. Your task is to translate the Spanish sentence into the English language.

¿En cuál de los fármacos con actividad antiviral aparece la base púrica denominada guanina?

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
In which of the drugs with antiviral activity does the purine base called guanine appear?