One Way to Be Sure That All "Groups" in an Experiment

Multiple Choice

One way to be sure that all "groups" in an experiment are equivalent except for their experience with the independent variables) is to use the same participants in all experimental conditions. However, this approach carries the danger of confounding in that

A) participants cannot participate in more than one condition.
B) random assignment of participants could not be done.
C) the sequence in which experimental conditions are experienced can affect performance.
D) with fewer different participants, results will not be statistically significant.