How does the adult female hard tick change after feeding?

The adult female hard tick significantly increases in size after feeding due to the enormous amount of blood it consumes from its host. This ingestion of blood causes the tick's body to expand, enabling it to store the nutrients necessary for the development of its eggs. Female ticks can often swell to several times their original size, making this a distinguishing characteristic of blood-feeding behavior in ticks. The change in size is a vital part of their reproductive cycle, as the nutrients garnered through feeding are essential for successful egg production.

While other options may mention changes in color or structure, they do not accurately reflect the primary transformation that occurs in female ticks post-feeding, which is the significant increase in size.