The correct answer is B) To keep the neoprene snugly fit around the shaft. The purpose of the spring in a lip-type oil seal is to provide a constant force that keeps the neoprene lip of the seal in tight contact with the shaft. This ensures a proper seal and prevents leakage of the lubricating oil. The spring helps maintain the seal even as the shaft rotates and the neoprene lip wears over time. The other answer choices are incorrect because: A) Removing burrs and dirt is not the primary function of the spring, C) Sealing against maximum fluid pressure is the role of the neoprene lip itself, not the spring, and D) Preventing air entry is not the purpose of the spring in an oil seal.