Select the most appropriate meaning of the underlined idiom in the given sentence.

Terrorists kill thousands of innocent people in cold blood.

cruelly, without any emotions

The most appropriate meaning of the underlined idiom "in cold blood" in the given sentence is cruelly, without any emotions.

The other options are incorrect.

• "In mountainous areas" does not mean cruelly, without any emotions. Mountainous areas are places with high altitudes and steep slopes.
• "By freezing to death" does not mean cruelly, without any emotions. Freezing to death is a natural process that happens when someone's body temperature drops below a certain point.
• "Accidentally" does not mean cruelly, without any emotions. Accidents are unintended events that happen by chance.

The idiom "in cold blood" comes from the idea of killing someone without any emotion, like a butcher killing an animal. In the same way, to kill someone in cold blood means to do so in a cruel and calculated way, without any regard for the victim's suffering. For example, you might say that a terrorist killed a group of people in cold blood.