Answer: D. I, II, and III.
Step-by-step explanation:
The demand for investment funds determines the demand for loanable funds and when this is higher than the supply, the rate increases. The reverse it true. It therefore affects real interest rates.
The savings of households and business firms are the source of loanable funds so if these are high relative to demand, the rate will decrease. The reverse is true.
Government demand for funds will increase interest rates as the supply will decrease when the government borrows massively. The reverse is true.
All three therefore impart real interest rates.