How much material is present in 1 part per million (ppm) of water?

1 part per million (ppm) refers to the concentration of a substance in a solution, indicating a ratio of 1 part of that substance to 1 million parts of the solution. In the context of water, if we consider 1 million pounds of water, 1 ppm would therefore represent the presence of 1 pound of material in that amount. This measurement is commonly used in environmental science and water quality assessments, helping convey the very small concentrations of substances in large quantities of water.

The other choices reflect different ratios that do not adhere to the definition of ppm. For instance, stating 1 pound of material per 1,000 pounds, 100 pounds, or 10,000 pounds of water misrepresents the standard ppm dilution, which is specifically 1 pound per 1 million pounds of water. Therefore, option C accurately captures the concept of ppm as it applies to water.