Fill in the blank with the most suitable word. The ______ heard that the relationship was stormy and had broken up several times.

inquiry

The most suitable word to fill in the blank is inquiry.

The sentence is about an investigation into a relationship. The only option that is related to an investigation is inquiry. The other options are impute, inordinate, and impugn, which are all related to making accusations or judgments.

Here is a more detailed explanation of the different options:

• Inquiry means a formal investigation into a matter. It is the most appropriate word to use in this context, as it conveys the meaning of someone looking into the relationship to find out more about it.
• Impute means to attribute something to someone, especially something bad. This is not the right word to use in this context, as it does not convey the same meaning as "inquiry."
• Inordinate means excessive or immoderate. This is not the right word to use in this context, as it does not convey the same meaning as "inquiry."
• Impugn means to attack or criticize someone's character or reputation. This is not the right word to use in this context, as it does not convey the same meaning as "inquiry."