When it comes to sex, do you think you know everything you need to know? We thought we did, until we took this quiz developed by Salon.com’s relationship columnist, Tracy Clark-Flory (a smart, insightful writer who was recently given her own sex advice column). We were pleasantly surprised to learn the percentage of married adults who are largely satisfied with their sexual partner, but chagrined to hear about the fastest-growing group of people with HIV in the U.S. (find out the answers to both questions by going to Salon.com). This test, which incorporates key knowledge that sex experts think most adults are lacking, will probably take you less time to complete than it takes the average couple to have sex (8 minutes -- and that's the only answer we're giving away).