I need help with number 15 please

Secondary pollutants are more harmful than primary pollutants. select the best answer from the choices provided ot of

Many farmers prefer cattle without horns because it is safer for their herds. the allele for no horns (n) is dominant to the allele for the presence of horns (n). a farmer mates a male with horns to a heterozygous female without horns. what is the chance that the offspring will have horns?

The hematodinium parasite becomes less of a problem for the blue crab when the crab is very young. fishing is thriving in the region. the crab moves to less salty water. a significant percentage of the population is impacted.