The network of glands that release chemical messengers directly into the bloodstream is called the endocrine system. The endocrine system produces and secretes t<span>hese chemical messengers, referred as </span>hormones directly into bloodstream to transmit signals to appropriate part of body. The hormones regulate bodily functions like growth, metabolism, <span>tissue function, sexual function, reproduction, </span>sleep and mood.
D would be the correct answer
The Hardy-Weinberg equation is:

where p generally represents the frequency of the homozygous dominant population.
The q usually represents the frequency of the homozygous recessive population, and the 2pq term represents the frequency of the heterozygous population.
Most things can't be explained or it hasn't been discovered yet. Science is all about asking questions and figuring out how things are the way they are.