Answer: performing on math tests, developing good work habits, and studying every night.
Explanation:
The event in the sentence is set in the present but will continue into the future. It would therefore be best to use a Present Continuous Tense for the underlined part to properly describe Cassie's actions as well as to introduce uniformity in the tenses used.
Present continuous tense would require the use of verbs with -ing which is why the best verbs to use are "performing", "developing", and "studying".
Mrs. Putnam gets it into her head that there must be a gigantic conspiracy between the Prince of Darkness and some of the supposedly God-fearing folk of Salem. That's what she means when she says "There are wheels within wheels in this village, and fires within fires!"
