The answer is D its tightly packed cells allow for proctection against harmful substances.
Answer:
Proteins
Explanation:
Generally just a guess so
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>
Cells are the basic unit of life and they are the 1st level of organization. The heart is the 3rd level. They are separated by 1 level, tissues.
