A structure composed of two or more tissue types that work together to perform specific functions for the body is a(n)

A. Proteins: Proteins serve as the primary structural components of cells and tissues. They form muscles, connective tissue, enzymes, and cell membranes, providing strength, support, and functional versatility throughout the body.

B. Carbohydrates: Carbohydrates primarily provide energy and serve as short-term fuel and structural components like glycogen, but they are not the main structural material of the body.

C. Lipids: Lipids function as energy storage, insulation, and components of cell membranes, but they do not provide the bulk structural framework of tissues.

D. Nucleic acids: Nucleic acids such as DNA and RNA store and transmit genetic information but do not serve as the primary structural material for the body.

A. Rubbing alcohol: Rubbing alcohol is a homogeneous solution of isopropyl alcohol and water. The molecules are evenly distributed, and no particles settle out over time. Because it does not separate, it is classified as a solution rather than a suspension.

B. Cytosol: Cytosol is the intracellular fluid that contains water, ions, and proteins in a dissolved or colloidal state. The particles remain dispersed and do not settle on standing. This makes cytosol more of a colloid or solution.

C. Blood: Blood is a suspension because it contains formed elements such as red blood cells, white blood cells, and platelets suspended in plasma. These components can separate out and settle if the sample is left undisturbed, fitting the definition of a suspension.

D. Salt water: Salt water is a solution formed when sodium and chloride ions completely dissolve in water. The ions remain evenly distributed and will not settle over time, which excludes it from being a suspension.