If we take the literal meaning of the sentence “glued to their seats” we can imagine that as they were glued they could not move, now if we read the information before this sentence “As they watched the performance unfold” we can infer that they were not able to moved due to the performance and the only way to do this is that the performance should be so interesting that gets all your attention. The answer is C) They were so interested that they did not move.
