Fourth Option: It introduces the topic and involves the reader in the activity.
Explanation:
Bob Kowalski in his article "A big Year" gives a slight clue to what the article is about i.e. <em>see a bird.</em> So it is about seeing birds. Another very important effect achieved by this line is that the writer engages the reader right from the beginning by directly addressing the reader. He creates a curiosity in reader's mind about why one needs to go the ends of the earth just to see a bird.
First option is incorrect because there is nothing such idea (birding being silly thing) neither in the first line nor anywhere in the article.
Second option is incorrect because the birders are not yet introduced in this line.
Third option is also incorrect because there is nothing such idea in the first line or anywhere in the article.
