The best statement that describes Ruby gathering enough evidence to support a scientific explanation concerning plant growth rates is:
"Ruby measures the heights of several species A, B, C, and D plants for a week under the same conditions and finds journal articles that describe the growth rates of each species."
This option indicates that Ruby is measuring the growth of all relevant species under controlled conditions, which is essential for making valid comparisons, and she is also consulting credible sources (journal articles) to support her findings.