Step-by-step explanation:
The word that does not mean "gradually" is C. abruptly.
The word "gradually" means progressing or developing slowly and steadily over time, which is synonymous with "steadily" and "slowly." "Progressively" also shares a similar meaning with "gradually," suggesting a step-by-step or incremental process.
However, "abruptly" means suddenly or unexpectedly, which is the opposite of a gradual process.