When to use an apostrophe to make a plural

Part of good writing is to be unambiguous. Sometimes you need an apostrophe to make a plural sound right. See the last word in this comic:


The apostrophe makes you pronounce it “prose” which is plural of “pro.” Without the apostrophe, it’s “pros,” which you might be inclined to pronounce “pross.”

This doesn’t happen very often. When I run into another example, I’ll post it.