Which scenario would result in an increase in productivity?

The total number of hours worked by the US labor force remains at 256 billion hours and the GDP stays at $20 trillion for the second year in a row.
The US economy’s GDP drops from $20 trillion to $19 trillion, but the total number of hours worked by the labor force remains at 256 billion hours.
The total number of hours worked by the US labor force increases from 256 billion hours to 285 billion hours, but the GDP stays at $20 trillion.
The US economy’s GDP grows from $20 trillion to $21 trillion, but the total number of hours worked by the labor force remains at 256 billion hours.

The scenario that would result in an increase in productivity is:

The total number of hours worked by the US labor force increases from 256 billion hours to 285 billion hours, but the GDP stays at $20 trillion.

This scenario indicates that the same amount of output (GDP) is being produced with fewer hours worked, indicating an increase in productivity.