Given a scientific question, generate a correct answer to it.

[Q]: Cardiac muscle is only found where?
[A]: heart

[Q]: Radioisotopes may vary greatly in their rate of decay, decaying faster if their nuclei are more what?
[A]: unstable

[Q]: Wings of bats and birds serve the same function. which body part should you study to understand ancestral differences?
[A]:
bones inside wings