Answer:
We could feed them with another type of food free of silver salts.
Explanation:
When talking about a phenocopy, we are referring to individuals who genotypically should be expressing a determined phenotype, but due to environmental influence, they express another phenotype. This is a non-inheritable phenotype, so it is not considered a mutation.
If we grow thy flies feeding them another type of food that does not include silver salts, and let them mate and reproduce, they will express the real phenotype, because they will not be influenced by the food. In the following generation, there will be dark individuals carrying the dominant allele, and yellow individuals, with the recessive genotype.
This is called homeostasis
<span>Some of the things that would make the experiment invalid would be, if there was a variation in the behavior of the class with respect to food - for example, if some people ate their breakfast earlier than the others. This then would mean that some students would have already digested their breakfast during the morning classes and the others would still be digesting. </span>