The correct answer is: C. Quantitative principle of money.
The quantitative principle of money is a theory that states that the value of currency is determined by the amount of money in circulation. This theory is based on the idea that the more money there is in circulation, the less valuable each individual unit of currency becomes.
The object principle of money is a theory that states that the value of currency is determined by the object that the currency is made of. This theory is based on the idea that people are willing to accept currency because it is made of a valuable material, such as gold or silver.
The state principle of money is a theory that states that the value of currency is determined by the government that issues the currency. This theory is based on the idea that people are willing to accept currency because the government has promised to back it with its full faith and credit.
None of the above is the correct answer because it does not represent a theory of money.