A hydrogen atom in an excited state emits a photon of frequency = 3. 199 x 1015 s-1. If the electron returns to the ground state, in which level was it before the photon was emitted?.

Tortoise shells and snail shells are similar in function: they protect the organism from predators. based on a comparison of the organisms in the images, what can you conclude? 1. tortoises and snails have homologous organs, and they’re evolutionarily related. 2. tortoises and snails have homologous organs, and they belong to same species. 3. tortoises and snails have analogous organs, and they belong to the same species. 4. tortoises and snails have analogous organs, and they don’t belong to the same species. 5. tortoises and snails have analogous organs, and they aren’t evolutionarily related.

Asoccer team has played 25 games and has won 60% of the games it has played. what is the minimum number of additional games the team must win in order to finish the season winning 80% of the games it has played?

Spider crabs live in the shallow regions of the ocean floor. algae tend to grow on the surface of spider crabs. the algae provide the crabs protection from predators by camouflaging them. the spider crabs give the algae shelter. what does this description suggest? 1. the algae are parasites of the spider crabs. 2. the algae and the spider crabs have a mutualistic relationship. 3. the spider crabs are commensals, and the algae are parasites. 4. the spider crabs benefit from the algae living on them. 5. the spider crabs are parasites of the algae.