A researcher noticed that as the prevalence of cell phone usage increased between the years of 1998 and 2010 so did the number of individuals diagnosed with autism. He decided that cell phone usage by expectant mothers was causing autism. Which of the following would NOT be helpful in evaluating his assumption?

A. The researcher should develop a clearly testable and falsifiable hypothesis.
B. The researcher should carefully design a reproducible experiment.
C. The researcher's experiment should include thousands of participants from all gender, socioeconomic, racial, and ethnic groups both with and without autism.
D. The researcher should use a small sample size (20 participants)of autistic children and their mothers to support the hypothesis.