Final answer:
The effect on GDP is an increase because Louis earned money by selling the sweaters.
Step-by-step explanation:
The correct answer is A. GDP increases because Louis earned money by selling the sweaters.
GDP, or Gross Domestic Product, is a measure of the total value of goods and services produced within a country's borders over a specific period of time.
When Louis sells the sweaters to the local store, he earns money from the transaction. This transaction represents economic activity and contributes to the nation's GDP.
Therefore, the effect on GDP is an increase because Louis earned money by selling the sweaters.