Let ${}_1,{}_2$ and ${}_3$ be the angular speed of the second hand, minute hand and hour hand of a smoothly running analog clock, respectively. If $x_1,x_2$ and $x_3$ are their respective angular distances in $1$ minute then the factor which remains constant $(k)$ is : $A\frac{{}_1}{x_1}=\frac{{}_2}{x_2}=\frac{{}_3}{x_3}=k$ B ${}_1{x}_1={}_2{x}_2={}_3{x}_3=k{}_1{x}_1^2={}_2{x}_2^2={}_3{x}_3^2=k$ D ${}_1^2{x}_1={}_2^2{x}_2={}_3^2{x}_3=k$