Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: Chlamydia is the most common STI in the United States. As shown in the graph in Figure below , females are much more likely than males to develop chlamydia. Like most STIs, rates of chlamydia are highest in teens and young adults. Answer: chlamydia
Which is the most common sti (sexually transmitted infection) in the united states?