Final answer:
Example 2 ('Quentin's father gave him a golden pocket watch; which was a priceless family heirloom.') incorrectly uses a semicolon where a comma should be used, as the clause following the semicolon doesn't stand as a complete sentence on its own.
Step-by-step explanation:
When analyzing sentences for correct mid-sentence punctuation, it is important to recognize that punctuation marks serve to clarify meaning, prevent ambiguity, and add emphasis or rhythm to a sentence. Incorrect punctuation can lead to sentence fragments, run-on sentences, and other errors that can make the writing less clear and harder to read. Sentence fragments are groups of words that fail to form a complete sentence either because they lack a subject, a verb, or both, or because they are punctured as if they were complete sentences when they are not. Run-on sentences occur when two or more complete sentences are incorrectly joined without proper punctuation or coordinating conjunctions.
Given that Example 1 ('The roof of that car was covered in Astroturf; a strange sight!') and Example 2 ('Quentin's father gave him a golden pocket watch; which was a priceless family heirloom.') both demonstrate incorrect punctuation, we can identify that Example 2 contains the error. A semicolon should not be used to introduce a clause that cannot stand alone as a complete sentence. The correct punctuation would be a comma, making the sentence 'Quentin's father gave him a golden pocket watch, which was a priceless family heirloom.' since the clause 'which was a priceless family heirloom' is additional information about the pocket watch and does not form a standalone sentence.