20.

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

one of ... is an apposition, for the explanation of principal dancer, so it needs to be separated by symbols. A dash here indicates emphasis.

Item F: There is no sentence after the period, wrong.

Item G: The semicolon is not a sentence, wrong.

Item J: The apposition here requires a comma or a dash, so the position of principal dancer is very clear, and the subsequent modifications are not limited.