Select the most appropriate option to substitute the underlined idiom in the…

Concept: An idiom is a fixed expression whose overall meaning is different from the literal meaning of its individual words. Substituting an idiom correctly means matching it to the single standard dictionary sense it carries as a whole, not to any one word inside it.

Application: The idiom "chop and change" means to repeatedly change one’s decisions, plans, or opinions instead of settling on one course of action (Cambridge Dictionary; Merriam-Webster). In the given sentence, the teacher’s instruction to stop "chopping and changing" and instead "make up my mind" is itself a restatement of that same idea — stop being indecisive and commit to one decision. This matches "making repeated changes in opinion".

Cross-check / Contrast: Each remaining option describes a different notion entirely:

• "avoiding the topic" describes evasion — sidestepping a subject rather than repeatedly changing a decision about it.

• "wasting time and energy" describes inefficiency — expending effort without productive result, not a pattern of switching opinions.

• "pursuing a mistaken or misguided course of action" describes staying on one flawed path, which is the opposite of repeatedly changing between options.

Since "make up my mind" in the sentence directly confirms the sense of indecision, and only one option names that sense, "making repeated changes in opinion" is the correct substitution.