Apostrophes have two different uses - the other one is to show that letters have been missed out so we have "We can't come", "We've arrived" and so forth. Short for "it is" we have "it's" and that's where the trouble starts. Something which it owns is "its", something which it is should be "it's" and there are no exceptions to this. Unfortunately, people don't seem to worry about the correct use of apostrophes any more, so that we have unacceptable and sometimes unintelligible texts which take a different view to correct one.
Meanwhile, plurals, things which in English often feature an s at the end of the word, don't need apostrophes. The apple's... suggests something belonging to one Braeburn rather than, say, a Gala and a Royal Gala together as the subject of a sentence.
I think it was Dave Barry who said that an apostrophe does not mean "Look out! An S is coming!" The sooner we learn that correct spelling and punctuation do still matter, the better it will be for literacy in schools, industry and elsewhere. We might even see less abominations in school exercise sheets before the pupils have attempted the questions. This week, I saw a sheet with plurals with apostrophes, a there/their error and a question without a question mark. Yes, it was the English section of the homework sheet. More next month.