Final answer:
Following a drought in the Great Plains, the price of wheat would rise due to reduced supply, leading to a decrease in the supply of bread and an increase in the demand for potato substitutes.
Step-by-step explanation:
If we assume a drought in the Great Plains reduces the supply of wheat, we would expect several effects on the market. Firstly, the price of wheat is likely to rise due to the decreased supply. Consequently, because wheat is a basic ingredient in the production of bread, the supply of bread is expected to decrease as the cost of its production increases. Lastly, considering potatoes are a consumer substitute for bread, with bread becoming more expensive and less available, it is logical that the demand for potatoes will increase as consumers look for alternatives.
Therefore, the correct response to what we would expect to happen is: a. the price of wheat to rise, the supply of bread to decrease, and the demand for potatoes to increase.