Answer:
Option B. All those who took the exam during the selected time period.
Step-by-step explanation:
The reason is that the population of interest is based on the people who took the exam during the selected period because it helps in estimating the actual economic benefits to the people who opted the MBA prgram. So basically we are using the earliar research papers which will help in understanding what value the MBA degree has generated. So the option B is correct.