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.
Bacteria !!!!!!!!!!!!!!!!!!!!!
D. Frederick Taylor because I learned it in class today and I searched it up
When an individual muscle fiber receives a threshold stimulus, it contracts as much as possible. ... a threshold stimulus is the minimum amount of energy needed to make a muscle fiber contract.
