Choose the correct idiom for the word highlighted in bold.
"The boss called the employees together for a meeting. He said he didn't know who was stealing from the company, but that he would leave no stone unturned until he found out who it was."

Correct option is C

Option (c) is the correct meaning of the given idiom.
Given Idiom: leave no stone unturned: To search exhaustively and use every possible method to achieve a goal or discover the truth; not to spare any effort. (Hindi: “कोई कसर नहीं छोड़ना / हर संभव प्रयास करना”)
Example: The auditors left no stone unturned to trace the missing funds.
Other related idioms and their meanings:
• Go the extra mile – put in more effort than expected (अतिरिक्त प्रयास करना).
• Hunt high and low – search everywhere (हर जगह तलाश करना).
• Pull out all the stops – use all available resources (सभी उपाय अपनाना).
• Burn the midnight oil – work late into the night (रात देर तक मेहनत करना).