If a Double-Blind Study Means That the Subject (Participant)and the Person

If a double-blind study means that the subject (participant) and the person administering the treatment do not know whether the treatment is the control or placebo,then what does a single-blind study mean?

A) that the subject (participant) does not know what s/he is getting- treatment or control
B) that the researcher does not know what the subject is getting
C) that the researcher,the assistant administering the treatment or control,and the subject (participant) all do not know what the subject is getting
D) There is no such thing as a single-blind study.