membrane proteins are not very soluble in water, because they possess long stretches of non-polar amino acids that are

Well, Saudi Arabia is known to be ruled by the Islamic law and is also known to not be a democracy (so options B and D are wrong).

Now, the head of the govenment is the king, and he is usually not  called "the supreme leader"... this is a term rather used in Iran.

So I think that the best answer is C. The royal family controls the government.(which is true!)