Which Statement Does NOT Describe a General Aspect of Signal $\alpha$

Which statement does NOT describe a general aspect of signal peptides?

A) They are often found at the N-terminus of secreted proteins.
B) They contain 10-15 hydrophobic amino acids.
C) They contain one or more negatively charged residues.
D) They tend to form an $\alpha$ -helical structure.
E) All of these are general aspects of signal pepides.