In the Equation $I _ { t } / \tilde { Y } _ { t } = \bar { a } _ { i } - \bar { b } \left( R _ { t } - \bar { r } \right)$

In the equation $I _ { t } / \tilde { Y } _ { t } = \bar { a } _ { i } - \bar { b } \left( R _ { t } - \bar { r } \right)$ , if $\bar { b }$
Is close to zero, investment:

A) is not very sensitive to real interest rate changes
B) is very sensitive to changes in the marginal product of capital
C) is very sensitive to real interest rate changes
D) is sensitive to tax rate changes
E) does not depend upon the real interest rate