Final answer:
A patent protects a drug manufacturer against competitors stealing its formula, providing exclusive rights to make, use, and sell the invention for usually 20 years.
Step-by-step explanation:
The form of intellectual property that protects a drug manufacturer against a rival stealing its formula is a patent. A patent grants the inventor an exclusive right to make, use, and sell the invention for a limited time, usually 20 years for pharmaceuticals. This exclusive right enables the firm to earn monopoly profits on its new drug by preventing other firms from manufacturing or selling it during the patent period. Although other forms of intellectual property exist, such as trademarks, copyrights, and trade secrets, the correct answer to the student's question is specifically a patent, which applies to inventions like drugs and their unique formulas.