((a)) A Reserve officer on active duty, other than for training, duty on a board, or duty of a limited or temporary nature if assigned to active duty from an inactive duty status, shall not be eligible for consideration for promotion under this subchapter; but shall be considered for promotion under chapter 21 of this title. If promoted while serving on active duty the officer shall be considered as having been promoted under this subchapter and shall be an extra number in the grade to which promoted for the purpose of grade distribution as prescribed in this subchapter. Upon release from active duty the officer shall be included in the grade distribution authorized by this subchapter.
((b)) Notwithstanding subsection (a) of this section, a Reserve officer who has been selected for promotion to the next higher grade under this subchapter at the time the officer reports for active duty, shall be promoted to that grade under chapter 21 of this title.
((c)) A Reserve officer who, at the time the officer is released from active duty, has been selected for promotion to the next higher grade under chapter 21 of this title, shall be promoted to that grade as though selected under this subchapter.
((d)) A failure of selection for promotion to the next higher grade occurring under this subchapter or under chapter 21 of this title shall count for all purposes.