Step 1: Understanding the Concept:
Pesticides are toxic chemical formulations designed to manage diverse non-insect vertebrate and invertebrate pests affecting agricultural storage and fields.
Step 2: Detailed Explanation:
Barium carbonate (\(\text{BaCO}_3\)) is an inorganic chemical compound that has been historically used as an effective, single-dose rodenticide (rat poison).
When ingested by rats or mice, it reacts with the hydrochloric acid in their stomach to form soluble barium chloride, which is highly toxic, causing muscle spasms, cardiac arrhythmias, and paralysis leading to death.
Step 3: Final Answer:
Barium carbonate is used as a rodenticide, which is option (C).