Which of the Following Is a Difference Between Single-Blind Studies

Which of the following is a difference between single-blind studies and double-blind studies?

A) Single-blind studies make use of naturally occurring groups, whereas double-blind studies randomly assign subjects to groups.
B) Single-blind studies occur when subtle cues are given by experimenters to the participants as to how they should behave, whereas double-blind studies occur when the behavior of the participants is influenced by the experimenter's knowledge.
C) In single-blind studies, participants do not know the experimental condition to which they have been assigned, whereas in double-blind studies, neither the participants nor the researchers know who has been assigned to which condition.
D) In single-blind studies, confounding variables are limited by independent and dependent variables, whereas in double-blind studies, the influence of confounding variables is not limited.