Answer: Option A
Explanation: If the qualities of two products that can be used in place of one another are very similar then they will be considered as perfect substitutes.
In case of perfect substitutes, if the price of good X rises then the demand for it substitute Y also rises. Hence the main factors affecting the demand will be the price as it will be the only factor that could influence the utility satisfaction of the consumer apart from the quality.
Hence, the correct option is A.
