The passage says that there is a large disparity in pay between the private and public sector. Because of this, many government administrators have left their job to take positions in the private sector. The passage suggests that if the public sector can raise salaries to a competitive level, these administrators will return to their government jobs and thus improve the functioning of public agencies.
The question asks you to identify what this position presupposes. In other words, what is the assumption being made in the passage? What gap in the passage's logic must we fill in with information?
Answer D is the correct answer. It says that people who moved from the government jobs to the private sector would choose to change careers again. In order for the position to be true, Answer D would also need to be true. Otherwise, raising pay in public agencies wouldn’t necessarily mean the return of those employees who left for the private sector. Maybe there are reasons why these employees would choose not to return to the government job even if the pay was competitive (more engaging work in the private sector, distaste for current government administration, etc). In order for the position taken in the passage to be true, we must presuppose that the government employees would be willing to change careers again if the government salaries became more competitive.
You are wondering why Answer C is not correct. Let’s take a look. Answer C says that unless government action is taken, the pay disparity between private and public sectors will only increase. This may or may not be true, but it isn’t necessary in order for the passage’s position to be logically sound. If the disparity did not continue to increase, but instead stayed the same that would not effect the logic the passage. The answer does not effect the key issue of whether these employees would actually return to their government jobs if the pay increased. Because Answer C does not address this hole in the passage’s logic, it is not the correct choice.
