Correct Response: A. To ensure the dissolved oxygen in the water samples is representative of the pond as a whole, several samples should be collected from different locations below the pond's surface, filled completely, and then sealed. This avoids collecting the most oxygenated water at the pond surface and it prevents oxygen from dissolving into the sample from air in the sample jar. Fast moving water from the surface that is near the pond's outlet (B) or inlet (D) will not be representative of the pond's water as the water samples will likely contain more dissolved oxygen. Similarly, the dissolved oxygen content of water samples that do not fill the jar and include organic matter from the bottom (C) may change over time and will likely not provide representative samples.
