The Market Segmentation Theory is the correct answer. This theory posits that the markets for different maturity bonds are completely segmented and that the interest rates for each segment are determined by the supply and demand within that segment. This means that the interest rates for short-term, medium-term, and long-term bonds are determined independently of each other. This theory aligns with Professor Hessen's statement that there is no relationship between short-term, medium-term, and long-term interest rates and that these rates are independently determined by the supply and demand in their specific bond markets. The Market Segmentation Theory also explains why certain investors, such as pension funds and insurance companies, prefer bonds of a certain maturity and are unlikely to switch from one maturity to another based on liquidity considerations.

Choice A is incorrect. The Expectation theory suggests that long-term interest rates are an average of expected future short-term rates, implying a direct relationship between short, medium and long term rates. This contradicts Professor Hessen's viewpoint which suggests these rates are independently determined.

Choice C is incorrect. The Liquidity preference theory posits that investors demand a premium for longer term bonds due to the increased risk associated with holding assets over a longer period of time. This implies an interrelationship between different term interest rates, which again contradicts Professor Hessen's viewpoint.