Which of the Following Describes a Characteristic of Single-Case Experimental

Which of the following describes a characteristic of single-case experimental design that allows researchers to examine causal effects of the intervention?

A) Studying the effect of the intervention on the dependent variable in only one subject at a time.
B) Randomly assigning either the baseline measure or the intervention for the single subject to start the experiment with.
C) Taking an initial baseline measure, followed by the intervention, then taking another measure after the intervention has worn off.
D) Isolates the main effect of the intervention using a reversal design, hence reducing complicated interaction effects that are confusing to interpret.