Acheetah ran 100 meters in 6 seconds. what is its average speed?

Which type of wave can travel without a medium

If steel is more dense that lake water, why can a boat float

Modern physics a photon emitted from an excited hydrogen atom has an energy of 3.02 electron volts. which electron energy-level transition would produce this photon? a. n=1 to n=6 b. n=2 to n=6 c. n=6 to n=1 d. n=6 to n=2 i chose b but the correct answer is d can someone tell me why? and what's the difference?