Read the passage below. In the blank, enter the single punctuation mark that correctly completes the sentence by setting off the nonessential element.
Answer:Discovered in a shipwreck off the Greek island of Antikythera, the remains of a complex bronze device have fascinated archaeologists since 1901. This device, a system of interlocking gearwheels dating back to the second century BCE【,】was used to track astronomical cycles with extraordinary precision. Historians consider it to be the earliest known analog computer, pre-dating similar European technology by more than a millennium.
Answer
A comma (,) must be placed in the blank.
The phrase 'a system of interlocking gearwheels dating back to the second century BCE' is a nonessential appositive modifying the subject 'This device'. Since the nonessential element is opened with a comma after 'device', it must be closed with a matching comma before the main verb 'was used' to prevent asymmetrical punctuation.
Step-by-Step Solution
Key Concept
Punctuation of Nonessential Elements