Need the answer to D

Will mark brainliest and 30 points

Identify the type of synthetic material used in each object

When the displacement of a mass on a spring is 12a the half of the amplitude, what fraction of the mechanical energy is kinetic energy? at what displacement, as a fraction of a, is the mechanical energy half kinetic and half potential?

Ryan is examining the energy of the particles in a bar of gold. what is ryan most likely studying?