#### Answer

$X+2Y\rightarrow XY_2$ best describes the reaction

#### Work Step by Step

By counting the particles in the diagram given, we can see that 3 units of $X$ react with 6 units of $Y$ to produce 3 units of $XY_2$. Simplifying this ratio gives 1 unit of $X$ reacting with 2 units of $Y$ to produce 1 unit of $XY_2$.