Consider the following statements:

1. Some claim to have seen UFOs (Unidentified Flying Objects).
2. Life on other heavenly bodies is considered to be a possibility.
3. Voyage to space is now an established fact.

From the above statements, it may be concluded that

The correct option is "Nothing definite can be said about the UFOs".

Let us analyze the given statements step-by-step to understand why this conclusion is correct:
1. Statement 1 states that "Some claim to have seen UFOs (Unidentified Flying Objects)." The keyword here is "claim." A claim does not establish a verified fact. It only tells us that some people believe or report having seen these objects, but it does not provide any confirmed data about what they actually are, where they originate, or if they even exist.
2. Statement 2 states that "Life on other heavenly bodies is considered to be a possibility." This indicates that extraterrestrial life is a hypothesis or a probability, not a certainty.
3. Statement 3 states that "Voyage to space is now an established fact." This confirms that human or robotic space travel is a reality, but it does not connect space travel to the origin or nature of UFOs.

Now, let us evaluate the given options based on these statements:
- "UFOs are heavenly bodies": None of the premises establish that UFOs are heavenly bodies. Statement 1 only mentions claims of sightings.
- "UFOs are sent from other heavenly bodies": There is no information linking the claims of UFO sightings to other heavenly bodies.
- "Some living species in other heavenly bodies are more intelligent than man": The statements do not discuss the intelligence level of any species, nor do they even confirm the existence of life on other heavenly bodies (calling it only a "possibility").
- "Nothing definite can be said about the UFOs": Since Statement 1 is based purely on unverified "claims" and none of the other statements provide concrete evidence regarding the origin, nature, or existence of UFOs, we cannot draw any definite or certain conclusion about them.

Therefore, it is logically sound to conclude that nothing definite can be said about the UFOs based on the provided premises.