If a radioactive substance starts at 100 grams and decays to 12.5 grams in 21.6 hours, what is the substance's half-life? a. 3 hours b. 7.2 hours c. 14.4 hours d. 21.6 hours

What is the importance of having the us forest service, the bureau of land management, the us fish and wildlife service, and the national park service? to manage land resources for conservation and the development of natural resources to manage land resources for conservation and the development of urban areas to preserve historical landmarks and manage the development of urban areas to preserve historical landmarks and manage the development of rural areas