Answer:
d. a restaurant buys a new wood-fired oven for baking pizzas
Explanation:
The national spending approach sometimes known as the spending approach. It is the method of finding out the GDP of a country by the calculating all the spending throughout the country which includes investment, consumption and spending.
Thus in the context, a restaurant owner buying a new wooden fired oven used for baking pizzas is considered an investment as it contributes to the national GDP of the economy when someone buys a product.