I think it's D as it was the overproduction not under production of goods that contributed to the great depression. Sorry if I'm wrong, that just seems like the logical answer
The best answer that describes conservation, as it applies to environment is choice B. It states that the economic use of natural resources in a careful, controlled way. Natural resource management includes land, water, soil, plants and animals with a specific focus on managing that affects the quality of life both present and the future.
The answer would be letter B.