Which of the following is true regarding Prediction of -Barrel Membrane Proteins?

• A. For membrane proteins with -strands only, the -strands forming the transmembrane segment are amphipathic in nature
• B. For membrane proteins with -strands only, the -strands forming the transmembrane segment are only hydrophilic in nature
• C. For membrane proteins with -strands only, the -strands forming the transmembrane segment are only hydrophobic in nature
• D. They contain six to nine residues