Final answer:
Roman Catholicism and Orthodox Christianity believe in purgatory, while Baptist and Seventh-day Adventist denominations do not.
Step-by-step explanation:
Among the given options, the Christian denominations that believe in purgatory are d. Roman Catholicism and a. Orthodox Christianity. Both Roman Catholicism and Orthodox Christianity teach the existence of purgatory as a place of purification and temporary punishment for sins before entering heaven. Purgatory is not recognized as a belief by Baptist and Seventh-day Adventist denominations.