Laughed... laughed would be the action being done in this sentence
I think the topic sentence is sentence 10.
Answer: Rainsford believed this because Zaroff stopped and his eyes climbed up the trunk of the tree. But his eyes stopped before he reached the limb where Rainsford lay and he smiled. Then he blew a smoke ring towards the tree and walked in the opposite direction. It’s obvious that Zaroff knew he was there, but was trying to prolong the game.
Kingsolver's tone shifts to more factual over page 50 and ahead.
Since its a sibling, and siblings tend to be in a person's close circle of people, informal speech is used.