D.
A fixed allele is homozygous within a population so D should be the correct answer.
Hope this helps!
SE LE CONOCE COMO IRRITABILIDAD
Los seres vivos tienen la capacidad de responder a una variedad de estímulos tanto del medio exterior como del medio interno. Esta capacidad de respuesta se denomina irritabilidad, porque es diferente a otro tipo de respuestas que se observan en la naturaleza.
Osmosis is 98% water and 2% salt inside the cell.
Energy stored in food can be used by cells to add a phosphate group to ADP to make ATP. This cycling of ATP to ADP occurs in a metabolic process called cellular respiration. phosphate group breaks, and energy is released. ATP becomes ADP, and the cycle of storing and releasing energy continues until the cell dies.