Answer : The most likely source of error in this experiment is the number of duckweeds in each beaker.
Explanation : As per the attachments, the number of duckweed plants that are placed in each beaker would be most likely the source of error in the performed experiment as it was the source of inaccurate results that was obtained. If this was the error that occurred during the experiment the results would largely vary because it is difficult to identify which of the plants grew when.
