Final answer:
Mrs. Saunders expresses her concern about 3) distinguishing between popular and right, the difficulty of staying true to oneself, and the negative consequences of blindly following a group.
Step-by-step explanation:
Mrs. Saunders is expressing her concern about 3) distinguishing between popular and right in relation to the Wave.
She is worried that Laurie's popularity and the power of the Wave are blurring the line between what is popular and what is morally right.
Mrs. Saunders feels that it is difficult for students to stay true to themselves and their own beliefs when they are caught up in the popularity and influence of the Wave.
She sees the Wave as a threat to individuality and integrity.
Overall, Mrs. Saunders is concerned about the negative consequences of blindly following a group and losing sight of one's personal values, which is the core idea behind her concern about the Wave.