Which one of the following statement is CORRECT for protein structure? Select one: a. For each natural amino acid sequence, there is a random unstable native state that under proper conditions is adopted by the help of ribosomes. b. Protein building blocks are chemically similar, and the structure of protein is, to a first approximation, uniform. O C. If a purified protein is heated, or otherwise brought to conditions far from the normal physiological environment, it will 'unfold' to a disordered and biologically-inactive structure. This change is irreversible and when normal conditions are restored, protein molecules will not readopt its native structure. d. The spontaneous folding of proteins to form their native states is the point at which nature makes the giant leap from the one-dimensional world of genetic and protein sequences to the three-dimensional world we inhabit.