Answer:
C. The waiting list for swimming lessons, which is always full, strangely had an opening this morning.
Explanation:
a <em>non-restrictive clause</em> is when you have a sentence, and you add more information that doesn't "restrict" the sentence using a set/pair of commas.
Ex. I was born in 2001, the year of 9/11, ... [here, I could add anything I want--which is why this is a non-restrictive clause]
complete example: We went to the zoo, my favorite place in the whole world, and learned about some neat animals.
So, we can see the use of two commas with information between them.
In the options given, <em> The waiting list for swimming lessons, which is always full, strangely had an opening this morning.</em>
is the sentence which uses a nonrestrictive clause correctly.
<em />
<em>Sentence: The waiting list for swimming lessons strangely had an opening this morning. </em>
<em>Added information: which is always full</em>
<em>together: The waiting list for swimming lessons, which is always full, strangely had an opening this morning.</em>
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hope this helps!! have a lovely day :)
