Random assignment is important to achieve in experimental research. Which of these research situations is an example of random assignment to conditions in a study?

a)Susie places the first six people to show up for her study in the experimental group and the next six people in the control group

b)Clarice has identified her population of interest as all students attending the local county high school. She then proceeds to randomly choose high school students for her study by having a random number generator generate possible high school ID numbers.

c)Every time a participant shows up for his study, Mark flips a coin to determine which condition to put the participant in. He predetermined that heads is the control group and tails is the experimental group.

d)Devon gives his problem-solving task to a group of first graders in the classroom for which he is a student teacher.