The answer is D. The natural selection is a theory which illustrates the gradual process of evolution in the population due to the change of environment. The key point is the mutation (variation) exists in the population before the environment changing. For C, if the environment does not change, though the adaptation is useful to environment, it will not be selected. Because the organisms without the adaptation will not die.
Answer:
A person who receives a gene for sickle cell disease from one parent and a normal gene from the other has a condition called "sickle cell trait." Sickle cell trait produces no symptoms or problems for most people. Sickle cell disease can neither be contracted nor passed on to another person.
Answer:
Water molecules are polar, so they outline hydrogen bonds. This gives water great properties, such as a for the most part high bubbling or boiling point, tall specific warm, cohesion, grasp, and thickness. Hydrogen has an electronegativity of 2.0, though oxygen has an electronegativity of 3.5. The refinement in electronegativities is 1.5, which infers that water can be a polar covalent molecule. In water, an electron from each of the hydrogen particles is drawn towards the oxygen particle. Protons, as unequivocally charged hydrogen particles, move outstandingly rapidly in water from one water molecule to the taking after, which is why the conductivity of water is modestly tall.
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