Final answer:
In "The Sacrificial Egg," a superstition is that a river spirit causes smallpox, and Julius is skeptical of this superstition, highlighting the clash between tradition and modernity.
Step-by-step explanation:
One superstition presented in "The Sacrificial Egg" by Chinua Achebe is the belief that a mythical river spirit, Kitikpa, is responsible for causing and spreading the smallpox epidemic in the village. Julius, the central character, is portrayed to be skeptical of such superstitions and tries to adopt a more modern way of thinking, which is in conflict with the traditional beliefs held by the villagers. His skepticism is reflective of the tension between old beliefs and new ways of thinking that are common themes in post-colonial literature.