8. Two numbers $\mathrm { x } , \mathrm { y }$ are randomly selected from the interval $[ 0,1 ]$. Let $p _ { 1 }$ be the probability of the event ``$x + y \leq \frac { 1 } { 2 }$'', and $P _ { 2 }$ be the probability of the event ``$x y \leq \frac { 1 } { 2 }$'', then\\
A. $p _ { 1 } < p _ { 2 } < \frac { 1 } { 2 }$\\
B. $p _ { 2 } < \frac { 1 } { 2 } < p _ { 1 }$\\
C. $\frac { 1 } { 2 } < p _ { 2 } < p _ { 1 }$\\
D. $p _ { 1 } < \frac { 1 } { 2 } < p _ { 2 }$