I think the correct answer would be option A. If researchers want to use eDNA to look for an invasive species in a waterway, then the first they should do would be to collect water samples from the waterway in question. In any experimental research, it is always collecting samples the first step before getting any results. You cannot execute experiments without any samples and consequently you will not have any results. For this problem, the researchers would not be able to stain the gel, compare the samples and cut the DNA when samples from the waterway are not collected.
