Answer:
The correct answer is option d.
Step-by-step explanation:
Suppose there is an economic growth the production possibility frontier will shift outwards. This will increase the production of both goods.
Suppose there is a technological advancement in the toy industry and no technological change in the greeting card industry. This means that the production of toys will require fewer resources. The excess resources can be used to increase the production of both toys and greeting cards.
Similar will be the case if there is a technological advancement in the greeting card industry and no change in the toy industry.