Why Did the British, When Defining the Iraq-Kuwait Border in 1923

Why did the British, when defining the Iraq-Kuwait border in 1923, give Kuwait more territory in the north than it traditionally controlled?

A) To reward Kuwait and encourage its further relations with the British
B) To restrict Iraq's access to the Persian Gulf
C) To assure Iran that the British did not favor Iraq over other states
D) All of these answers are correct.