Final answer:
The nonrestrictive clause in the sentence provided is 'when it gets cold'. This type of clause offers additional information that is not necessary for the sentence's main point and can be removed without changing the sentence's essential meaning.
Step-by-step explanation:
The nonrestrictive clause in the sentence "In December - when it gets cold - I like to use a soft warm blanket" is 'when it gets cold'. A nonrestrictive clause, also known as a nonessential clause, is a part of a sentence that provides extra information and can be removed without changing the essential meaning of the sentence.
In this sentence, 'when it gets cold' adds additional information about the time period 'In December' but is not essential to the overall meaning. It simply provides context. If you remove this clause, the sentence still makes sense: "In December, I like to use a soft warm blanket".
What Are Nonrestrictive Clauses?
Nonrestrictive clauses are set off from the rest of the sentence with commas or dashes because they are not integral to the structure of the core sentence. Removing a nonrestrictive clause does not change the sentence’s basic meaning, but it may delete useful details. In contrast, a restrictive clause is fundamental to a sentence's meaning and cannot be removed without altering the sentence's core message.