Idioms and Phrases - Verbal and Reasoning

In the following questions four alternatives are given for the idiom/phraseitalicised and underlinedin the sentence. Choose the alternative which best expresses the meaning of idiom/phrase.
Q1:

The detective left no stone unturned to trace the culprit.

A took no pains

B did very irrelevant things

C resorted to illegitimate practices

D used all available means

ANS:D - used all available means

No answer description is available.