About how much of the united states is covered by forests? a 90%b 10%c 50%d 30%

the transfer of energy between two molecules spaced just nanometers apart plays a key role in many technologies, including photovoltaics, quantum information systems, lighting, and sensors, as well as in biophysics to measure nanometer distances and in photosynthesis. but an open question in this area is what effect, if any, the surrounding photonic environment has on this nanoscale energy transfer. by designing and performing a carefully controlled experiment to answer this question, scientists have settled the debate and found clues to improving the efficiency of many of the technologies that rely on this process.

explanation:

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.