Nobody likes to think about -- much less talk about -- sexually transmitted diseases. That's one of the reasons STDs are spread so easily. Shame, embarrassment, or just plain denial can keep people from seeing their doctors or talking to their partners when they suspect they might have an STD. But the cost of remaining silent can be high. Many STDs, chlamydia included, can cause serious complications if they remain untreated. Take our quiz and see how much you know about this rapidly spreading health threat.