Choose the correct meaning of the following idiom:

A bone of contention

A reason for discord

The correct meaning of the idiom "a bone of contention" is a reason for discord. It is a matter that is disputed or argued about, and that can cause disagreement or conflict. The idiom is thought to have originated from the practice of dogs fighting over a bone, which is a source of conflict.

The other options are incorrect. "Bone of lion" is a nonsensical phrase. "Cause of friendship" means something that brings people together. "Continue to bed" means to go to bed.