I'm guessing the word that is italicized capacious because in this case it is synonymous with vast, meaning that he has a developed mind with broad views.
The word that best defines the italicized word (capacious) from the novel Frankenstein is vast. The last option is correct.
Capacious can be defined as having a lot of space inside; roomy.
Vast means of very great extent or quantity; immense.
Frankenstein; or, The Modern Prometheus is a novel written by English author Mary Shelley that follows the story of Victor Frankenstein, a young scientist who creates a hideous creature in an unorthodox scientific experiment.
