The diagram below shows a change in the production possibility frontier (PPF) of an economy that produces digital services and automotive manufacturing.

The movement of the production possibility frontier from AB AB\,AB to AC AC\,AC is most likely to have been caused by:
a rise in consumer preference and market demand for manufactured vehicles.
a nationwide increase in the labor force participation rate.
the introduction of advanced robotic automation on vehicle assembly lines.
a transfer of existing capital equipment from the digital sector to the automotive sector.