4. The collision of a comet and a planet is an ______ event in that it occurs only rarely.
Answer: D
Exceptional
The collision of a comet and a planet is an exceptional event in that it occurs only rarely. This term accurately captures the infrequency and unusual nature of such occurrences in the cosmos.
A) Inferior
The term inferior does not apply in this context, as it generally refers to something of lower quality or status. A comet colliding with a planet is not a matter of quality but rather a matter of occurrence frequency, making this option incorrect.
B) Ordinary
Describing the event as ordinary implies that it occurs frequently, which contradicts the definition of the collision being rare. Thus, this option is incorrect as it fails to represent the uniqueness of such events.
C) Understandable
While the term understandable suggests that the event can be comprehended, it does not address the rarity of comet-planet collisions. Therefore, this option does not accurately reflect the context of the question and is incorrect.
D) Exceptional
Exceptional is the appropriate term to describe the rare occurrence of a comet colliding with a planet. This word signifies that such events are out of the ordinary and happen infrequently, aligning perfectly with the context provided in the question.
Conclusion
Exceptional is the definitive correct answer as it highlights the rarity and unusual nature of comet-planet collisions, which is the crux of the question. The other options fail to convey this essential characteristic, making them unsuitable in this context.