Option D is the answer because Edward feels responsible for his best friend's divorce even though he had nothing to do with it. One of the symptoms of depression is the feeling of worthlessness and guilt. Edward is feeling guilty.
Sickle hemoglobin differs from normal hemoglobin by a single amino acid: valine replaces glutamate at position 6 on the surface of the beta chain. Therefore the red blood cell bends differently giving it a sickle shape
the name porifera means pore bearer in latin. a sponges body is covered by a skin, one cell thick. this skin has lots of small pores ad a few large openings. the small openings are the entrances to a complex system of channels. these collar cells pump water through the entire sponge and filter out food for the sponge cell to eat
