Which of the following drugs is an antiemetic?

Metoclopramide Hydrochloride is the correct choice for an antiemetic because it works by blocking dopamine receptors in the brain that trigger nausea and vomiting. This action makes it effective in treating conditions such as postoperative nausea and vomiting, as well as nausea associated with chemotherapy.

The other options serve different purposes: Baclofen is a muscle relaxant used primarily to treat spasticity; Amoxicillin Trihydrate is an antibiotic effective against bacterial infections; and Folic Acid is a type of B vitamin important for cell division and is commonly used in supplement form during pregnancy to prevent neural tube defects. Each of these medications has distinct therapeutic effects unrelated to the prevention or treatment of nausea and vomiting, which is the specific role of antiemetics like Metoclopramide.