What process has been used for centuries by farmers to produce the breeds that most suit their needs?

a.
creating mutations

b.
gene therapy

c.
selective breeding

d.
genetic engineering

The answer is C. selective breeding. This is a process by which certain individuals with desirable traits are bred to create offspring who (hopefully!) share the same desirable traits. If the farmers select individuals carefully, they should be able to eradicate the presence of all undesirable traits after a couple of generations.
Hope that helped you.

The basic building blocks of dna and rna are nucleotides