1.B. Childrens' shoes are on the bottom three shelves. - it should be children's
2. C. Ours' is surely the most colorful float in the parade. - it should be ours, without the apostrophe
3. D. Both Shira and Kate's feet were sore after the long hike. - it should be Shira's and Kate's feet, because they don't share the same feet
4. A. There's not a dimes worth of difference between the two models. - it should be dime's
5. C. Theres a red gate at the park's entrance. - it should be there's
6. I'm not sure who's purse is on that chair. - it should be whose
7. I don't know about this one, sorry :/
8. A. Yes, that 65 convertible is considered a classic. - it should be '65
9. B. The dogs tail is wagging very quickly. - it should be dog's
My standard would be based on how it affected those it need, how accessible the invention/charity/etc was, and how they plan to grow in the future. Hope this helps!
