Answer:
a. substitutes
b.increase
c. Complements
d. falls
Step-by-step explanation:
A substitute or substitute good is a product or service that can be easily replaced with another. In other words, its a product or services a consumer sees as the same or similar to another product.
Due to a fall in price of any commodity, the demand for such commodity is going to increase.
A Complementary good is a good whose use is related to the use of an associated or paired good. Two goods are complementary if using more of good A requires the use of more of good B