I think the answer is a but if not I am sorry
The sentence that should appear first in an effective summary of Part 2 of "The Adventure of the Blue Carbuncle" is A. The owner of the hat, Henry Baker, pays a visit to Holmes after spotting the advertisement in the newspaper.
<h3>What is summary?</h3>
It should be noted that summary simply means a concise information about a particular happening or event
In this case, the sentence that should appear first in an effective summary of Part 2 of "The Adventure of the Blue Carbuncle" is that the owner of the hat, Henry Baker, pays a visit to Holmes after spotting the advertisement in the newspaper. This is important for the text sequence.
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A.to organise
B.join
2A.to help
B.donate
3.A.to protect
B.cutting
4.A to reduce the
B. walking