Assume you have a vector $x=[5,4,9,3,1]$ in MATLAB. You want to create a new vector $y$ that contains all elements of $x$ but in reverse order. Which of the following commands accomplishes this?

A$.y=$flip$(x)$

B$.,y=$reverse$(x)$

C$.$ end :$-1$:$1$

D$.y=x(-1)$