7. Two numbers $x$ and $y$ are randomly chosen from the interval $[0,1]$. Let $p_1$ be the probability of the event ``$x + y \geq \frac{1}{2}$'', $p_2$ be the probability of the event ``$|x - y| \leq \frac{1}{2}$'', and $p_3$ be the probability of the event ``$xy \leq \frac{1}{2}$''. Then\\
A. $p_1 < p_2 < p_3$\\
B. $p_2 < p_3 < p_1$\\
C. $p_3 < p_1 < p_2$\\
D. $p_3 < p_2 < p_1$