D. They're the main site of photosynthesis in autotrophs.
Organism that can make their own food
A chemical change is a change that results in new chemicals (the reactants underwent a chemical change which resulted in new products).
an example of a chemical change is the burning of paper. An example of something that is not a chemical change is the melting of ice.
Answer is: <span>Sound waves travel faster in more dense material, and the more dense the material the louder the sound is.
</span>Sound travels approximately fifteen times faster through the metal railway tracks than through air. <span>The </span>speed of sound is faster in solid materials and slower in liquids or gases. The denser is material, t<span>he closer are the molecules to each other and the less time it takes to molecules to pass the sound to each other and sound is faster.</span>