Idiomatic preposition – governance of "put one's own house … order": fill the blank with the correct preposition. Base sentence: "The ruling party will have to put its own house _____ order." Instruction: Choose the preposition that completes this fixed expression. Final instruction: Select the option that is idiomatic in standard English.

Given data

• Expression: put one's (own) house _____ order.

Concept/Approach
The fixed phrase is put (one's) house in order, meaning to organize one's affairs properly, often before criticizing others.

Option analysis
in — correct preposition in the idiom. ✅on / to / into — not used with this idiom; they change or break the set expression. ❌

Example
The ministry must put its house in order before launching new initiatives.

Final Answer
in