The Diagram Below Show the Market for Financial Capital Assuming

The diagram below show the market for financial capital assuming that national income is constant at potential GDP,Y*.
FIGURE 25-2
-Refer to Figure 25-2.Suppose national saving is reflected by NS 0 and investment demand is reflected by I0D.Now suppose the government implements a revenue-neutral tax policy that encourages investment.What is the effect on the real interest rate?

A) There is no effect on NS or ID,and the interest rate remains at i*.
B) National saving shifts to NS1,and the real interest rate falls to i3.
C) The real interest rate rises because of the decrease in the budget surplus.
D) The real interest rate falls because of the decrease in the budget surplus.
E) Investment demand shifts to I1D,and the real interest rate rises to i2.