A Man Has a Sexual Encounter During Which His Partner

A man has a sexual encounter during which his partner passes the AIDS virus to him. The virus becomes established in his body, but he remains asymptomatic. Does this man have an STI (sexually transmitted infection) or an STD (sexually transmitted disease) ?

A) Neither; he is asymptomatic.
B) Both; an STI is the same as an STD.
C) An STI; he has an infection but no symptoms.
D) An STD; he has an infection that causes a disease.
E) An STD; he has an infection that can be transmitted.