Answer:
An effective price ceiling on coffee would cause the demand curve for lemons to shift to the left.
Step-by-step explanation:
An effective price ceiling results in lower prices, increased demand, and shortages. Since tea and lemons are complement, a decrease in the price of coffee (substitute of tea) would result in a decrease in the demand for lemons (complement of tea). This means that the demand curve for lemons will shift to the left.