Interest rates in the economy are determined primarily by the supply of capital (loanable funds) and the demand for capital , as explained in the Investment Funds in Canada (CIFC) text under Economic Factors and Financial Markets. The course states that “ interest rates are influenced by changes in the supply and demand for money ,” and that an increase in the supply of capital , all else being equal, will place downward pressure on interest rates .

When capital supply increases, there is more money available for lending from sources such as households, corporations, pension funds, insurance companies, and governments running budget surpluses. With more funds competing to be lent, lenders are willing to accept lower interest rates in order to attract borrowers. This inverse relationship between capital supply and interest rates is a foundational concept in CIFC economics.

The other options all result in higher , not lower, interest rates according to CIFC principles. An increase in default risk leads lenders to demand higher returns to compensate for the added risk. Increased business activity raises demand for borrowing, which pushes interest rates upward. Similarly, higher inflation erodes purchasing power, so lenders require higher nominal interest rates to maintain real returns.

Therefore, only an increase in capital supply leads to lower interest rates, making Option C the correct and fully verified answer based on the Investment Funds in Canada curriculum.