Calculate the wavelength, in nanometers, of the light emitted by a hydrogen atom when its electron falls from the n = 7 to the n = 4 principal energy level.

Give an example of the type and scale of economic activity for a traditional economy.

In the image, layer a is the topmost layer. layer c contains fossils from the precambrian era. layer b contains dinosaur fossils, and layer a contains fossils of mammals. which two statements are supported by this evidence? 1. mammals lived before the precambrian era. 2. dinosaurs and mammals existed in the precambrian era. 3. dinosaurs evolved after precambrian organisms. 4. precambrian organisms evolved after dinosaurs. 5. precambrian organisms were the first life-forms to become fossilized, according to this sample.

The graph shows the populations of two species in a particular region over two decades. based on the graph, what can you conclude about the relationship between the two species? a. the two species have a parasitic relationship. b. the two species are mutualistic in nature. c. the two species exhibit commensalism. d. the two species have a prey-predator relationship. e. the two species have a familial relationship.