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?
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.
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.