C.
It is hard for soil to become fertile when it can not get water from the rain, and high temperatures would cause any water the soil does get to evaporate.
The sugar found in DNA contains one less oxygen molecule than the sugar found in RNA.
Anticipating that one is about to eat can trigger the cephalic phase of digestion.
The cephalic phase of digestion is the stage during which the stomach responds to the mere sight, smell, taste as well as thought of food. Approximately 20% of total acid secretion takes place before food reaches the stomach.
During this phase of digestion, gastric acid and pepsinogen secretion is activated by the thought, sight or smell of food and also when food is inside the mouth.
The cephalic phase of gastric secretion is moderated completely through the parasympathetic nervous system. A variety of sensory stimuli including the sight, smell, and taste of food induces acid secretion in the stomach.
To learn more about parasympathetic nervous system here
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D. Natural selection
is your correct answer.
