Select the most appropriate meaning of the given idiom.

Fit as a fiddle

Healthy and strong

The most appropriate meaning of the idiom "fit as a fiddle" is healthy and strong.

The other options are incorrect.

• "Of the right size" is not the same as being healthy and strong. A fiddle can be any size, and being the right size does not necessarily mean being healthy and strong.
• "Singing happily" is not the same as being healthy and strong. A person can be healthy and strong without singing happily.
• "Playing a musical instrument" is not the same as being healthy and strong. A person can be healthy and strong without playing a musical instrument.

The idiom "fit as a fiddle" comes from the fact that a well-tuned fiddle is able to produce a clear, strong sound. So, when someone is said to be "fit as a fiddle", it means that they are in good physical condition and have a lot of energy.