Final answer:
The short story 'Dr. Heidegger's Experiment' by Nathaniel Hawthorne prominently features the themes of Time and Regret, and Power and Greed, depicting how characters reflect on their past and demonstrate the corrupting nature of greed when they regain their youth.
Step-by-step explanation:
Universal Themes in 'Dr. Heidegger's Experiment'
The short story 'Dr. Heidegger's Experiment' by Nathaniel Hawthorne explores several universal themes. However, referring to the options provided, the most prevalent themes in the story would be Time and Regret (b) as well as Power and Greed (c). The theme of time and regret is evident through the characters' reflections on their lost youth and the mistakes they've made in their lives, as well as through the supernatural experiment that briefly restores their youth. They ruefully consider how their lives could have been different if they had retained their youth and vitality. At the same time, power and greed are depicted in the way the characters behave once they regain their youth; they quickly fall back into their old, selfish ways, showcasing how greed and desire for power can corrupt individuals.
Literature during the Romantic period often grappled with these themes, showing a fascination with natural beauty, human emotions, and philosophical reflections on existence, as highlighted by writers such as Friedrich von Schiller and Sir Walter Scott. The power of nature and beauty, as well as the consequences of human actions, are common threads within romantic literature, contributing to a broader understanding of the human experience.