Let I = E - DR Represent an Investment Function

Let I = e - dR represent an investment function. The coefficient d

A) should always be positive and larger in magnitude if a 1-point increase in R causes a relatively large change in investment.
B) should always be negative and larger in magnitude if a 1-point increase in R causes a relatively large change in investment.
C) should always be positive and smaller in magnitude if a 1-point increase in R causes a relatively large change in investment.
D) should always be negative and smaller in magnitude if a 1-point increase in R causes a relatively large change in investment.
E) can have either sign depending on circumstance.