Topic: Group verb,

Best Answer Explained in Below-:

The phrase "He ran into debt" is an idiomatic expression that means he accumulated debt, often unexpectedly or unintentionally. The preposition "into" indicates a transition or movement from one state to another, in this case from a state of financial stability to one of being in debt. The expression conveys the idea that he found himself in a situation of financial liability.

On the other hand, in the sentence "You should not run into debt," the same idiomatic structure is used to advise against accumulating debt. Here, "into" serves a crucial role, emphasizing the action of entering a state that is generally viewed as negative—debt. The other options provided do not appropriately fit the context of the sentences. For instance, "on" and "after" do not convey the necessary transition into debt, while "for" incorrectly suggests a purpose rather than a change in financial status. Therefore, "into" is the correct choice, aligning with the specific meanings conveyed in both sentences, making it clear that both individuals are discussing the implications of becoming indebted.