Use of prepositions in strings of conjunctions
When one wants to list various cases/classes/categories/types of objects in a string of conjunctions, is it preferable (or even mandatory) to keep on using (the same) preposition in front of each one them?
Moreover, does singular or plural form of the word "case", "class", "category" make any difference in the previous question?
Examples:
In the present article, we study the case of X, of Y and of Z objects.
(in this example, as in most of the ones I have in mind, it is the preposition "of" which is relevant to my question).We study the cases/classes of X and of Y objects.
vs.
We study the cases/classes of X and Y objects.
Although it is rather clear that, in the singular case, the absence of "of" in later conjuncts may lead to a logical confusion (e.g., mistakenly taken as the one class/case of objects which are both X and Y), when it comes to plural of the words "case", "class", etc., this might not be an issue. Still, there might anyway be a rule in the plural setting as well.
Solution 1:
According to William Strunk's Elements of Style (Chapter 3, suggestion 15), "an article or a preposition applying to all the members of a series must either be used only before the first term or else be repeated before each term."
In other words, either approach is acceptable as long as you remain consistent.
I'd say that in general the prepositions should be omitted unless you want to emphasize that the items in the list are separate.
Solution 2:
As long as the prepositions before each object are the same, it's both easier to parse and stylistically preferred to not repeat the preposition.
In the present article, we study the case of X, Y and Z objects.
Repeating the of in this example, as you did above, actually decreases my comprehension, as I have to spend a small amount of mental energy to properly construct the coordination.
The only time that I would repeat the preposition is when it differs:
In the present article, we examine the objects from X, for Y, and within Z.