I believe it’s add a semi colon after ring
The sentence with correct comma use is: C. "You have twenty minutes," she said, "before the show begins."
In the story, we know that Sergei uses his wishes for the goods of others,
The first one is to cure his sister's lung cancer, the second one is to cure his son's mental problems
Based on this, i think we can conclude that sergei has a kind hard and always want to help those around him without regards for himself
hope this helps
<span>Add: This is just one example of the benefits schools get from offering music classes to their students.
This sentence follow best because it references, specifically, offering music classes versus "music students" which is inaccurate. It implies there are other benefits beyond just graduation rate, which most would agree there are (cultural, etc).</span>