Q17:

As a large corporation in a small country, Hachnut wants its managers to have international experience, so each year it sponsors management education abroad for its management trainees.  Hachnut has found, however, that the attrition rate of graduates from this program is very high, with many of them leaving Hachnut to join competing firms soon after completing the program.  Hachnut does use performance during the program as a criterion in deciding among candidates for management positions, but both this function and the goal of providing international experience could be achieved in other ways.  Therefore, if the attrition problem cannot be successfully addressed, Hachnut should discontinue the sponsorship program. 

In the argument given, the two boldfaced portions play which of the following roles? 

1. The first describes a practice that the argument seeks to justify; the second states a judgment that is used in support of a justification for that practice.
2. The first describes a practice that the argument seeks to explain; the second presents part of the argument’s explanation of that practice.
3. The first introduces a practice that the argument seeks to evaluate; the second provides grounds for holding that the practice cannot achieve its objective.
4. The first introduces a policy that the argument seeks to evaluate; the second provides grounds for holding that the policy is not needed. (D)
5. The first introduces a consideration supporting a policy that the argument seeks to evaluate; the second provides evidence for concluding that the policy should be abandoned.

请问C为什么不可以?