Two students completed an experiment to determine if pesticide use at local farms was causing fish kills in a local pond. The steps of the experiment are listed below. Select one location to collect water samples in the pond. Collect a 5-mL water sample at 8 am for two days. Measure the amount of pesticide present in each sample using the same measurement tools. After analyzing their data, the students conclude that pesticide runoff from farms is not causing the fish to die in the pond. Which of these statements best describes why their conclusion is not reliable? The pesticide measurements were the dependent variable. The samples were collected at different times. The samples were only collected for two days. The time of sample collection was not an independent variable.