Identify the error in the use of the underlined pronoun

What is the difference between a major and a minor character? a major character has a less important story line, while a minor character plays a bigger role in the plot. a major character plays a big role in the plot, while a minor character has a less important story line. a major character has an unimportant story line in the plot. a minor character's story line is as important and developed as the major characters' story lines.

How do i can change this sentence : a modern physician in a small town not only is proficient in general medicine but surgery as well. to parallel structure?

Review the detail. beethoven chooses to stay when the children beg him to play more. which is the best inference that can be drawn about beethoven?