6. Three points, $P, Q$ and $R$ are placed on the circumference of a circle with centre $O$. The arc lengths $P Q, Q R$ and $R P$ are in the ratio $1: 2: 3$.
In what ratio are the areas of the sectors $P O Q, Q O R$ and $R O P$ ?
A $1: 1: 1$
B $1: 2: 3$
C $1: \pi: \pi^{2}$
D $1: 4: 9$
E $1: 8: 27$