Explanation:

The Production Possibility Curve (PPC) represents the maximum output combinations of two goods that an economy can produce with its given resources and technology. It shows the trade-offs a society faces when allocating resources between two goods.

Downward Sloping PPC:
The PPC is downward sloping due to the concept of opportunity cost. As an economy produces more of one good, it must give up increasing amounts of the other good. This is because resources are not equally efficient in producing both goods. Thus, the opportunity cost of producing more of one good is the forgone production of the other good.

Concave PPC:
The correct answer is option A, which states that the PPC is concave to the origin. This means that the slope of the PPC is decreasing as we move from left to right along the curve. In other words, the opportunity cost of producing an additional unit of one good increases as more of that good is produced.

Reasoning:
- The concave shape of the PPC reflects the concept of diminishing marginal returns. As an economy reallocates its resources from one good to another, the additional output gained from each additional unit of resources decreases.
- For example, if an economy is initially producing only consumer goods and decides to produce some capital goods instead, the first few units of capital goods produced will have a high opportunity cost in terms of the forgone production of consumer goods. However, as more capital goods are produced, the opportunity cost of producing additional units of capital goods decreases because resources are not equally efficient in producing both goods.
- This concave shape of the PPC indicates that an economy can achieve more efficient production by specializing in the production of goods for which it has a comparative advantage.

Conclusion:
In conclusion, the PPC is downward sloping and concave to the origin. This shape reflects the concept of opportunity cost and diminishing marginal returns. It highlights the trade-offs and choices an economy faces when allocating its scarce resources between different goods.