C is the correct answer i think, because scientist do not consider them as living since they lack the properties that all living organisms have or should have
 
        
             
        
        
        
Homeostasis: A state of balance reached through reactions within a cell or organism. 
Metabolism: The total of all chemical reactions within an organism.
Organism: Any living thing that takes in food, grows, and reproduces.
        
             
        
        
        
Complete Question:
Which of the following might stimulate the cephalic phase of gastric secretion?
A. stomach distention
B. the production of saliva
C. the thought of food
D. the production and secretion of gastrin. 
Answer:
C. the thought of food
Explanation:
Gastric secretion usually occurs in three different phases, namely;
- Cephalic 
- Gastric 
- Intestinal 
The thought of food usually stimulate the cephalic phase of gastric secretion in organisms. The presence of lipids or low pH inhibits Gastric secretion during the intestinal phase. 
 
        
             
        
        
        
The answer is vitamin D. This is actually a group of vitamins of similar molecular structure responsible for facilitating increased absorption of calcium, magnesium and phosphate from the gut. The most important of the vitamin D compounds are vitamin D3 and D2. While vitamin D can be obtained from your diet and supplements, the major source of vitamin D is from a chemical reaction dependent on skin exposure to the sun.