German singer Nadja Benaissa was charged with causing grievous bodily harm to a man who contracted H.I.V. after having unprotected sex with her admitted in court on Monday that she had concealed the fact that she was infected with the virus from the man, and from two other sexual partners.

Do you think you know all there is to know about safe sex? According to a landmark study of people ages 18-29, many young adults have some seriously dangerous assumptions and beliefs about pregnancy and STD prevention.