Humans Carry All of the Genes Necessary to Develop a Tail

Multiple Choice

Humans carry all of the genes necessary to develop a tail, but we typically don't develop tails because:

A) those genes are never activated.
B) those genes can only be activated by external factors that no longer exist in our present environment.
C) we have also inherited a copy of the dominant "no tails" gene.
D) we have also inherited two recessive "no tails" genes.