​In Randomized Controlled Trials, Researchers Assign Participants to Treatment or Control

Multiple Choice

​In randomized controlled trials, researchers assign participants to treatment or control groups randomly. What is the best definition of "random" as it applies to this?

A) ​Group assignment is haphazard and not systematic.
B) ​Participants are unaware of their group assignment.
C) ​Researchers are unaware of the group assignments
D) ​Everyone has an equal chance in group assignment.