According to the author

The correct option is: "any research result can be of value to an intelligent investigator."

Step-by-step Explanation:
1. Understanding the Role of an Investigator: An intelligent investigator possesses the critical thinking skills, analytical tools, and background knowledge necessary to synthesize information. They do not look at data in isolation; instead, they connect new findings to existing frameworks.
2. The Potential of Research: Even if a research result seems minor, negative, or inconclusive at first glance, it holds potential value. A negative result can steer an investigator away from a dead end, and a minor finding might serve as the missing piece of a larger puzzle. Therefore, "any" research result has the inherent capacity to be useful.
3. Analyzing the Nuance of Modals:
- The options containing absolute terms like "always" or "must always" are too restrictive and logically flawed, as they assume guaranteed utility under every possible circumstance.
- The option stating "not many research results" is overly pessimistic and underestimates the capability of an active, intelligent mind to find meaning in diverse data.
- The correct option uses the modal verb "can", which correctly highlights the possibility and potential of any research finding to yield value when analyzed by the right mind.