The distinction between flexible and fixed individual differences: is that managers have little or no impact on flexible differences. is that managers should hire people based on their attitudes and emotions. is that managers have little or no impact on fixed differences. has no practical value for managers.

The distinction between flexible and fixed individual differences is that managers have little or no impact on fixed differences. Fixed differences in this case are often differences where the person who exhibits a certain characteristic is also the person who won't be changing them so soon. And this is a thing where managers have little say over it. 

What was the length to begin with?