Final answer:
The formal and scientific tone in H.G. Wells's passage is due to the educated language and factual references to planetary development, particularly involving life beginning on Mars and the cooling process of planets.
Step-by-step explanation:
The tone of the passage from H. G. Wells is considered formal and scientific primarily because the narrator uses well-informed language and cites facts about planetary development, aligning with option C: The narrator quotes facts about Mars and sounds well educated. The formal tone is reflected through the use of technical terms related to the nebular hypothesis, the concept of life beginning on Mars, and considerations of the cooling process of celestial bodies in relation to the emergence of life.