Amyloid fibrils are associated with many fatal degenerative diseases of humans and livestock. Livestock diseases such as scrapie in sheep and bovine spongiform encephalitis (BSE, or mad cow disease) have major negative impacts on agriculture. Human diseases characterized by amyloid fibrils include Alzheimer's disease and Creutzfeldt-Jakob disease. Choose the true statements about amyloid fibrils.

a. Amyloid fibrils have a high amount of β-sheet structure.
b. Proteins that convert to an amyloid structure form soluble fibrils.
c. Because most newly synthesized proteins fold correctly, the accumulation of misfolded proteins (or fragments) tends to occur slowly, thus explaining the slow onset of disease.
d. An amyloid fibril is stabilized by hydrogen bonds between small hydrophilic residues.
e. Proteins that form amyloid fibrils are normally soluble.