For which of the following functions is f(q+b)=f(q)+f(b) for all positive numbers q and b? Choose the correct option.
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(q+b)=f(q)+f(b) Its e) f(x)= -3x
<result>E</result>
For which of the following functions is f(q+b)=f(q)+f(b) for all positive numbers q and b?