Statement A is incorrect. The passage does not suggest that the values of all things would remain constant; instead, it highlights that the value of money would change.

Statement B is incorrect. The passage does not imply that the values of things sold would be doubled, only that their prices would increase.

Statement C is incorrect. The passage does not discuss halving the value of things bought, but rather focuses on the value of money being halved.

Statement D is correct. The passage indicates that if the prices of all things doubled, the value of money would be halved. This is because money would have less purchasing power, meaning that the same amount of money would buy fewer goods and services.