Final answer:
The correct answer to which category is ranked the least amount of emphasis is D. None of the above, as the options provided do not pertain to the emphasis on management categories of staffing, planning, or controlling.
Step-by-step explanation:
The question asks which category is ranked the least amount of emphasis. If we reference the given options - individual performance cannot be evaluated and the task is easy - against the categories of staffing, planning, and controlling, we can conclude that these options are not directly related to the level of emphasis on a management category.
Thus, the correct answer is D. None of the above. The question provides options that don't inherently lend themselves to any hierarchy or ranking of emphasis among the management functions. Therefore, none of the given categories can be singularly determined as having the least emphasis based on the information provided in options a and b.