Hi Thestorea! The correct answer would be 5 W's +1 H. The apostrophe is needed when showing the plural of lowercase and uppercase letters to prevent forming a word. Example: "I got 3 A's last semester." (would be correct-not "3 As").

In general, the apostrophe is not needed. I think you will find that some people add an apostrophe for clarity if omitting it would cause confusion, but this would be an ad hoc solution to an awkward situation. The article that one responder posted is from the American Psychological Association Style Guide, but there are many different style guides. If you work for a company that has adopted a style guide, you should use the one that was adopted.

Neither is correct, it should be "5 Ws + 1 H". An apostrophe is not appropriate here.