A verb in the indicative mood is one that states a fact or asks a question. In the provided passage, you can find a verb in the indicative mood in:
Sentence 20: "The Grand Canyon is visited by almost five million people each year."
This sentence states a fact about the number of visitors to the Grand Canyon.
Therefore, the correct response is Sentence 20.
(Note: The exact numbering may vary depending on the original source, where Sentence 20 in this context may correspond to the one indicating visitor statistics.)