The correct answer is proteins.
Proteins have four structures; (1) primary, (2) secondary, (3) tertiary, and (4) quaternary. Primary structures of proteins are formation of peptides and the peptide bonds between amino acids. Secondary structures of proteins involves the amino acid composition leading to hydrophobic interactions forming either alpha helices or beta sheets. Interactions between secondary structures of proteins will make the tertiary structure which is either soluble (globular) or insoluble (fibrous) proteins. Quaternary structures are the combination of two or more tertiary structures and these are called subunits.
My guess is that it is tundra, but i'm not completely sure.
A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time.
True if you are talking about an isotonic solution
