They come from the atmosphere, since plants use carbon dioxide to produce carbohydrates :)
I guess the answer is B !! as it has no relevance and is not an observation !!
B) Photosynthesis The Sun is the ultimate source of all energy in the universe. Plants being the main primary producers or autotrophs, use solar energy to make their own food through photosynthesis, thus converting energy into the organic matter that can be consumed by all organisms. They form the basis of almost all food chains from where consumers derive their food.
In physical geography<span>, a </span>dune<span> is a </span>hill<span> of loose </span>sand<span> built by </span>wind<span> or the flow of water.</span><span> Dunes occur in different shapes and sizes, formed by interaction with the flow of air or water. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind. The valley or trough between dunes is called a </span>slack<span>. A "dune field" is an area covered by extensive sand dunes. Dunes occur, for example, in some </span>deserts<span> and along some coasts.</span>
