Which of the following is a possible reason that urban sprawl is common even when it has a negative impact on the environment? a. extending outward causes more crowded conditions b. extending outward is more economical than extending upward c. extending outward creates less pollution d. all of the above

Consider hydrogen in an excited state n = 5n=5 that emits photons to reach the ground state. there are various possible transitions other than straight to the ground state that can occur; for example, it can drop to the n = 3n=3 state followed by the n = 3n=3 to the ground state transition. which of the possible transitions will result in the emission of a photon in the visible region?