Final answer:
The sentence 'The cat napped in the garden among the roses' is the best application of the advice, using 'among' correctly to refer to undistinguished parts of a collective group.
Step-by-step explanation:
Among the provided sentences, "The cat napped in the garden among the roses" best applies the advice from the usage guide. This sentence correctly uses among because it refers to an undistinguished part of a collective group - the roses in the garden. The cat is at rest within the collective mass of the roses, which is an appropriate context for the word among.
In contrast, "Janaya strolled between the crowds of the city" and "The ship sailed between the tossing waves" are inappropriate use of between because they suggest moving through distinct, countable entities, but in these sentences, the entities are actually uncountable or viewed collectively. "Tom debated among giving his brother gloves or a book" is also incorrect since among is used with uncountable or non-distinct items, and here the items (gloves or a book) are very distinct.