tortillafactory has to say the following:
Honk if your so horny you can't spell proparlee.
Seriously. HOW DIFFICULT IS IT? I always like to sing Strong Bad's song:
"If you want to be possessive, it's just I T S! But if you want it to be a contraction, it's I T apostrophe S!" Not very helpful, but funny anyway.
Which in turn provokes the following comment from tashabear:
We did a conga line in Language Arts once, chanting "Yes, yes! Apostrophe S! Singular possessive is Apostrophe S!"
(It was a small school.)