What is the central idea of the of this story? "the cold equation"

In the story, "The Cold Equations" by Tom Godwin, it has central ideas which show restraint or restriction, a battle between choices which something is said to be dangerous or forbidden, whilst a hero tries to reject or disregard the restriction but ultimately the tale comes into a tragic end. The theme of this story is that an individual must be sacrificed so that others would survive.

Istrongly feel d is the answer but c is also a strong possibility