Let's solve each given equation for $a$

Take: $\frac{a}{xs}$$=632$
Multiply both sides of the equation by $xs$ to get: $a=632xs$

Take: $\frac{a}{ys}$$=158$
Multiply both sides of the equation by $ys$ to get: $a=158ys$

Since both equations are set equal to $a$, we can write: $632xs=158ys$
Divide both sides of the equation by $s$ to get: $632x=158y$
Divide both sides of the equation by $158$ to get: $4x=y$

Now we can replace y with 4x in Quantity B to get :
Quantity A: $x$
Quantity B: $4x$

At this point we can see that, if x = 1, then Quantity B is greater
Conversely, if x = -1, then Quantity A is greater

Answer: D