Which statement is true of a reversible reaction at equilibrium? '

Only the forward reaction is taking place.

When a reversible reaction initially starts, the formation of products from reactants is the only reaction observed.

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.