A shift in demand occurs when an influencing factor other than price changes. Those factors are:

- The income of buyers

- The tastes and preferences of buyers

- The prices of other goods and services, especially substitutes and complements

- Expectations of buyer about the future

In this question:

- 'Prices of complementary goods decrease' will lead to quantity demanded for that complements rising, then demand for consumer good will increase accordingly.

- 'Price of the consumer good decreases' will increase the quantity demanded for that good, but it will not shift the demand curve

- 'Customers' expectation of higher prices in the future': in this scenario, customers tend to buy more to store in present, which leads to demand curve shifting to the right

- 'Consumer tastes shift toward substitute products': Demand for substitutes will rise, so demand for that consumer good will decrease and the demand curve shifts to the left.

LO 2, AC 2.2