The diagram illustrates production possibility curves (PPC) for an economy making two goods, sweet potatoes and onions. At the start, the economy is functioning on PPC$_1$. Which pair of changes could move PPC$_1$ to PPC$_2$?
- Achange 1: a fuller use of existing resources in onion farms; change 2: a reduction in the price of sweet potatoes
- Bchange 1: a reduction in the price of onions; change 2: a larger population in the country
- Cchange 1: an increase in the price of sweet potatoes; change 2: an increased consumer preference for onions
- Dchange 1: an increase in the training of onion farmers; change 2: a greater use of technology on onion farms