Which of the Following Is True of Integral Membrane Proteins

Which of the following is true of integral membrane proteins?

A) Both the inner and outer surfaces involve primarily hydrophilic groups.
B) Both the inner and outer surfaces involve primarily hydrophobic groups.
C) The outer surface involves primarily hydrophilic groups and most of the hydrophobic groups must turn inward.
D) The outer surface involves primarily hydrophobic groups and most of the hydrophilic groups must turn inward.