Which of the following statements best describes why new copper extraction methods are needed?

The correct option is High-grade copper ores are becoming scarce.. This answer is correct because it matches the approved learning objective to explain that metal ores are limited resources in the subtopic Alternative methods of extracting metals.

The correct option is High-grade copper ores are becoming scarce.. High-grade copper ores are becoming scarce. is correct because it directly supports the approved learning objective to explain that metal ores are limited resources. This belongs to the subtopic Alternative methods of extracting metals within Using the Earth's resources and obtaining potable water, so the explanation must stay tied to that curriculum context. The other options are incorrect because they either do not answer this learning objective, use a vague statement, or move away from Alternative methods of extracting metals.