In the following questions, four alternatives are given for the Idiom/Phrase printed in bold in the sentence. Choose the alternative which best expresses the meaning of the Idiom/ Phrase.

To let off steam , my friend started murmuring.

A. to release his tension

B. to show his anger

C. to show his approval

D. to show his disple

Please do not use chat terms. Example: avoid using "grt" instead of "great".