Which choice completes the text so that it conforms to the conventions of Standard English?
The mosque, one that has seen consistent attendance since it was first constructed, has a sound system ____ surprisingly modern, replete with all of the latest equipment.
[correct answer: A]
priority level - we all want this one
If you clicked on (B), and it wasn’t a mis-click, then you want to know a cool, direct thing about dashes.
If you clicked on (D), a great thing to memorize about colons is that what comes before a colon should be a complete sentence. Knowing this is one confident way to eliminate (D).
If you clicked on (A), which is the correct final answer, solely by instinct, this is a very valid route to have taken.
If you clicked on (C), it would be understandable if the presence of other commas within the sentence drew you to this option. Learning more about how the test writers particularly seem to use commas is one way to secure a similar question to this one in the future. That said, for many of us, this is a very ok misfire today, as mastering comma usage within questions takes a fair amount of experience.
bonus
We have statistics tied to how often the correct answer to a question testing punctuation is the option with no punctuation.