E.g. I think "11. Columbus's ships arrived in North America in 1492." is ambiguous. He reached an island that is in the region commonly called [link|http://en.wikipedia.org/wiki/North_America|North America], but not the mainland. Geographically, he reached the Caribbean Plate.

I wasn't positive about "17. Choose the sentence that has a dangling modifier:
- Being very patriotic, the flag inspires me every day.
- After the party, Ted went home to sleep.
- While walking to the store, I saw the craziest thing.
- He decided to wear those shoes, which had been stored away since last winter." but the last one seemed to be the obvious choice to me.

There doesn't seem to be an all-in-one-place list of answers for the 21 questions.

Cheers,
Scott.