(b) is answer.
If $A\to B$ then for each same value of $A$, $B$ value should be same. If all the $A$ values are distinct the FD hold irrespective of the $B$ values.
Since all $Y$ values are distinct FDs with $Y, YX$ and $YZ$ on LHS hold. So, option $B$ is correct.
In option A, $Z \to Y$ is violated as for same $Z$ value we have different $Y$ values.
Similarly in C, $X \to Z$ is violated and in D, $XZ \to Y$ is violated.