The gold standard of a research study includes aspects like showing superiority, blinding, randomization, and treatment & control groups. What are some examples of studies that would not be able to fit this standard? (Select all that apply.)
Options:
A. If you are studying a rare disease or disorder with a very small patient population.
B. Conducting a study using a procedure that is observable (such as a surgical procedure).
C. If you are conducting a study on a disease or disorder with a high mortality rate.
D. All of the above.