The idiom "walking on thin ice'' means doing something risky or dangerous that could lead to trouble. Step 1: Analyze options
- (A) Walking carefully on a thin surface: literal meaning, not idiomatic.
- (B) Engaging in risky behavior: correct idiomatic meaning.
- (C) In a dangerous or precarious situation: close but broader than idiomatic use.
- (D) Walking gracefully on a slippery surface: incorrect meaning.
Thus, the idiomatic meaning is best captured by option (B).