Is the standard deviation of the salaries of Company Y s

This one is straight E. No need to look for examples.

"Standard deviation shows how much variation there is from the mean. A low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values."

We know only that mean(Y)>mean(Z) and median(Y)>median(Z) - absolutely useless info to compare SD's.

But still if you need an example:
Consider company Y to have one employee with a salary of $10, so SD(Y)=0 (if Range or SD of a list is 0, then the list will contain all identical elements. And vise versa: if a list contains all identical elements then the range and SD of a list is 0. If the list contains 1 element: Range is zero and SD is zero) and company Z to have two employees with a salaries of $1 and $2, so SD(Z)>0: mean(Y)>mean(Z) and median(Y)>median(Z) but SD(Z)>SD(Y)=0;

Now, consider company Y to have two employees with a salaries of $10 and $11, so SD(Y)>0 and company Z to have one employee with a salary of $1, so SD(Z)=0: mean(Y)>mean(Z) and median(Y)>median(Z) but SD(Y)>SD(Z)=0.

For more on standard deviation check:
SD chapter of Math Book: math-standard-deviation-87905.html
PS questions on SD: ps-questions-about-standard-deviation-85897.html
DS questions on SD: ds-questions-about-standard-deviation-85896.html

Hope it helps.