OK, I'm finally tackling one of the dreaded apostrophe homophones. Took two years to build up the courage... and think of appropriate illustrations. And I'm still not 100% sure I nailed it. Leave a comment, I really want to know what you think of this one.
I figure a tandem bike implies dual ownership – Their bike, rather than his or hers – even if they aren't pictured. (Besides, the fewer times I show them, the fewer times I can be accused of implying that They're doing something in that panel.)
The next one seems pretty self-explanatory to me. The rider is pointing to the bike – There it is.
Finally, They're riding it. Yes, they are.
I dunno. Works for me. What about you?