Fifty-Five People Volunteered to Participate in a Statistical Study

Fifty-five people volunteered to participate in a statistical study. For each volunteer, a coin was tossed. If the coin landed tails up, the volunteer was assigned to group 1. If the coin landed heads up, the volunteer was assigned to group 2. Those in group 1 were asked to eat carrot salad daily for 1 year. Those in group 2 were asked not to eat carrot salad for 1 year. At the end of the year, the progress in improving vision was significantly higher for group 1 than for group 2. Did the study use a random selection from some population? Did the study use random assignment to experimental groups? ​

A) The study used random selection and random assignment.
B) The study did not use random selection and random assignment.
C) The study used random selection but did not use random assignment.
D) The study used random assignment but did not use random selection.