The diagram illustrates production possibility curves (PPC) for an economy producing two goods: sweet potatoes and onions. At first, the economy is operating on PPC$_1$. Which combination 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