Find the odd musical instrument (keyboard vs string family): Pick the option that is not a string instrument.

Introduction / Context:
Instrument families are typically grouped by the primary sound source. Violin, Guitar, and Sitar are string instruments where vibrating strings produce sound directly, while a Piano is a keyboard instrument with hammered strings and a distinct classification by playing interface and ensemble role.

Given Data / Assumptions:

• Violin: bowed string instrument.
• Guitar: plucked string instrument.
• Sitar: plucked string instrument from Indian classical music.
• Piano: keyboard instrument where hammers strike strings; commonly classified under keyboards in orchestration contexts.

Concept / Approach:
Although piano contains strings, its primary interface and family in most curricula is the keyboard family, contrasted with hand-played chordophones. Thus it separates cleanly from three hand-played string instruments.

Step-by-Step Solution:

Verification / Alternative check:
Consider performance practice: piano uses keys and hammers, unlike the direct finger contact with strings in the other three.

Why Other Options Are Wrong:
They are all directly actuated string instruments without a keyboard interface.

Common Pitfalls:
Do not confuse internal construction with family classification; the playing interface matters for grouping.

Final Answer:
Piano