Question: Fill in the blanks in the passage with the most appropriate set of words from the options for each blank.
The best punctuation is that of which the reader is least conscious, for when punctuation, or lack of it, _____ itself, it is usually because it _____.
The sentence has opposing clauses. If the reader is least conscious, then the punctuation is good, if there is lack of punctuation or more of it, then, it should make the reader take notice(or if it obstructs or obtrudes). That he or she would if it offends or is glaringly missing or present. That gives us our answer as choice 1.
Hence, the correct answer is option 1.