It would be Nemo because that's who Dory is giving the leaf, or the direct object, to. You can think of it as the indirect object bouncing back from the direct object.
Excuse me if i'm wrong, but I believe its B.
A topic is the main idea of a writing. In this case, the topic of the essay is Yellowstone National Park because the essay talks about the national park itself.
<span>Anne Hutchinson and Roger Williams were both banished from their colonies. They were forced to leave and shunned until they did so.</span>