Why Are Hydropathy Plots NOT Usually Used to Detect Transmembrane $\beta$

Why are hydropathy plots NOT usually used to detect transmembrane $\beta$ strands in porins?

A) The length of a transmembrane $\beta$ strand is typically shorter than that of an $\beta$ helix.
B) Amino acids in transmembrane $\beta$ strands in porins may not be exclusively hydrophobic.
C) Amino acid side chains project away from the polypeptide in a $\beta$ sheet
D) Answers A and B are both correct.
E) All of the answers are correct.