A fish breeder wishes to develop a silver goldfish. She starts with a diverse mixture of fish, some more silver than others. Generation after generation, she allows only the most silver fish to breed. After 30 years of work she has a new breed of fish with interesting traits, but on average, the fish are no more silvery than other goldfish. Which of the following would be a logical explanation for her failure?

There is no variation for the trait (silver coloration).
Silver coloration is an environmentally-determined trait.
The selection was artificial, not natural, so it did not produce evolutionary change.
There was no selection (differential reproductive success) related to silver coloration.
The breeder accidentally picked less silver fish when she meant to pick more silver fish.