Final answer:
Ambassador posts are likely to be included in the Plum Book as they are political appointments by the president. The Plum Book lists positions subject to noncompetitive appointment and does not include regular civil service positions or other irrelevant personal information.
Step-by-step explanation:
The Plum Book is a publication that lists over 7,000 federal civil service leadership and support positions in the legislative and executive branches of the United States government that may be subject to noncompetitive appointment, typically by the president. The purpose of the Plum Book is to identify positions that can be filled by the president's political appointees. Therefore, in the options provided, the positions likely to be included in the Plum Book are ambassador posts (c), as these are political appointments made by the president and often change with a new administration.
Positions such as postal carriers (a) are part of the regular civil service system and not typically considered political appointments. Doctors at a VA hospital (b) are also part of the civil service. Senate committee chairs (d) are elected by members of the Senate and are not appointed by the president, whereas the phone numbers of a Congress member's sex partners (e) would be entirely irrelevant and inappropriate to include in a government publication.