The Pet Peeves Of the Frustrated Author, Part 4

Most possessives use an apostrophe. "Its" is the possessive exception that proves the rule.

"It's" is always, and only, a contraction for "it is." Thus, "It's fun to beat people with a morning star."

"Its" is the possessive. Thus, "I prefer the morning star weapon, because its spikes tear human flesh to shreds."

I'd be less violent about my examples if the fucking ENGLISH TEACHER who just emailed me hadn't been the wrongest wrong that ever wronged in print.