Answer:
B. Demand for a product rises and the supply of the product falls.
Step-by-step explanation:
When the supply of a product is scarce and the demand for it is high, it increases in value and therefore the price of it goes up.
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If the demand for a products falls along with its supply, the price won't rise at all. If anything, It'd decrease.
If the demand isn't high, the price won't rise no matter how much supply it has. Additionally, if it's high in stock the it's value won't be as high.
Again, when the supply is high in stock, the product's value won't be as high even if the demand is high, since there's a plentiful amount of it.
Thus, the best option is B.
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