Idioms at the end of ring characters

Idioms with the fourth word "Huan", four-character idioms with the last word ending in "Huan" and their explanations;

Vicious circle-many bad things are mutually causal, endless and getting worse.

The oriole wears a silver ring to repay her kindness. Refers to repay a debt of gratitude.

Knot a knot in the grass-an ancient metaphor, expressing gratitude and gratitude, and never forget it until death.

Sparrow's title ring-as a reward for kindness.