In reverse genetics, what is the correct order in which the experimenter proceeds?

A$.$ silencing the genes in question using RNAi, followed by mapping to locate the gene

B$.$ identification of a gene of interest followed by screening for mutations in that gene and studies of the phenotypes caused those mutations.

C$.$ selection of mutants with a phenotype of interest and then mapping to locate the effected gene$($s$)$

D$.$ random mutagenesis, followed by observation of offspring for newly acquired traits