Why would a light wave speed up if it moved from air into hydrogen

Which organelles are labeled d, and what is one feature that distinguishes them from the other labeled organelles chloroplasts the only organelles that produce sugars from sunlight mosomes, only found in animal and bacterial cells centricles only found in animal cells mitochondra, the only energo-generating structures found in cells

Give three examples of plant activities that are affected by circadian rhythms and natural fluctuations in the length of daylight?

Which of the following types of stars are dim but can have high surface temperatures? giants main sequence stars supergiants dwarfs