Question

what question did early naturalists have when they first encountered cnidarians? are they plants or animals? how fast can they swim? how deep do they live? are they dangerous to humans?

Explanation:

Early naturalists were primarily concerned with basic classification. Cnidarians (like jellyfish, corals) have some plant - like appearances (e.g., corals can look like underwater 'plants'). Classification into kingdoms (plant vs animal) was a fundamental early question in natural history. The other questions (swimming speed, depth of living, danger to humans) are more complex, specialized, and likely came after the basic classification question.

Answer:

Are they plants or animals?