Answer:
A) Dave's production function changed.
Step-by-step explanation:
When Dave expanded his hot dog business, his production function didn't change at all. The production function shows the relationship between the amount of inputs used and total output, its basically a math equation.
In order for the production function to change, the proportion of capital and labor must change. But in this case, total output will double because the amount of labor and carts will double, not because productivity increases.
The production function changes only when productivity changes.