(a) Part A The sentence that best states a theme of the passage is:
B: Adventure can occur unexpectedly.
(b) Part B The detail from the passage that best supports the answer to Part A is:
C: ". . . and was just in time to see it pop down a large rabbit-hole under the hedge." (paragraph 3)
This detail highlights how Alice's unexpected encounter with the White Rabbit leads her to adventure as she runs after it and follows it down the rabbit hole.