Answer: Option C
Explanation:
In this case Dionne if she posts an internal vacancy she can however fill the position but she has to recruit another person to fill that person's vacancy. This is the challenge that Ty manager has referred to. So anyway it is necessary to recruit candidate externally. This would also double the work for Dionne.
The training has to be done for two people if one is internally recruited. The choices to the position are limited when it is internal. If the vacancy is filled up through external sources then training of one person is sufficient and it will be productive and cost saving method.