The following molecule acts as an:

According to the NCERT Chemistry Class 12 textbook (Chapter: Chemistry in Everyday Life), the given structure corresponds to Brompheniramine.

Brompheniramine belongs to the class of drugs known as antihistamines. Antihistamines act by competing with histamine for its receptor sites, thereby preventing histamine from producing its physiological effects. As a result, they are commonly used to relieve symptoms associated with allergic reactions, such as sneezing, itching, runny nose, and watery eyes.

Hence, the given compound is classified as an anti-histamine.

Correct Answer: Option D - Anti-histamine.