What motion of the skeleton involves lifting your arms towards the sky and then lowering your arms to your sides?

abduction and adduction

opposition

flexion and extension

circumduction

flexion and extension

no it's abduction and adduction

Apologies for the confusion. You are correct. The motion of lifting your arms towards the sky and then lowering them to your sides involves abduction (lifting the arms away from the body) and adduction (bringing the arms back down towards the sides of the body). Thank you for pointing that out.