How do enzymes affect reactions?
o
a. enzymes are used up in reactions.
o
b. enzymes cause reactions that normally release energy to absorb
energy
o
c. enzymes prevent reactions from occurring.
o
d. enzymes lower the activation energy required for reactions to
occur.

it,s D

Explanation:

Enzymes are known as biological catalyst and work by lowering the activation energy of a reaction. They do this by providing an alternative pathway which speeds up the reaction without the catalyst undergoing a permanent change. ... An important thing to remember is that enzymes do not affect the equilibrium of a reaction.

The most likely explanation for the variation is the offspring were produced from different combination of genes. A single pair of gold fish mentioned in the question means a male and a female gold fish. The two of them mated and contributed different genes to the fertilized fish eggs, this results in production of various body shape and colouration which is known as variation.