Final answer:
Propofol is the anesthetic agent among the given options that is administered intravenously, commonly used for both the induction and maintenance of anesthesia in a surgical setting.
Step-by-step explanation:
The anesthetic agent that is administered intravenously from the options given is Propofol. Anesthetic agents are drugs that are used to induce general anesthesia, and they can be either as gases or vapors (inhalational anesthetics), or as injections (intravenous or intramuscular anesthetics). Nitrous oxide, Halothane, and Isoflurane are typically known as inhalational anesthetics and are generally administered through inhalation using an anesthesia machine. On the other hand, Propofol is a widely-used intravenous anesthetic known for its rapid effect and is commonly used for the induction and maintenance of anesthesia in surgical settings.