When an electron in an atom moves from high to low energy levels:
a alpha particles are emitted
b gamma rays are emitted
c energy is emitted as electromagnetic radiation
d energy is absorbed

energy is emitted as electromagnetic radiy

Explanation:

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

i'm pretty sure its b i might be wrong though!