For which of the following functions is f(e+b)=f(e)+f(b) for all positive numbers e and b?  Choose the correct choice from the following answers.
A) a) f(x)=x^2  B) b) f(x)=x+1  C) c) f(x)=root x  D) d) f(x)=2/x  E) e) f(x)= -3x
f(e+b)=f(e)+f(b) Its e) f(x)= -3x
<result>E</result>
For which of the following functions is f(e+b)=f(e)+f(b) for all positive numbers e and b?