Which of these statements is completely true about the wt situation above?
a. gene z is expressed in the presence of stimulus a and blocked in the absence of a
b. gene z is blocked in the presence of stimulus a and expressed in the absence of a
c. gene z is blocked in the presence of stimulus a and blocked in the absence of a
d. gene z is expressed in the presence of a and expressed in the absence of a
e. none of the above

Whenever diploid populations are in hardy-weinberg equilibrium at a particular locus a) the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change. b) natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency. c) this means that, at this locus, two alleles are present in equal proportions. d) the population itself is not evolving, but individuals within the population may be evolving.