Let `f(x)` be defined for all `x > 0` and be continuous. Let `f(x)` satisfies `f(x/y)=f(x)-f(y)` for all `x,y and f(e)=1.` Then (a) `f(x)` is bounded (b) `f(1/x)vec 0` as `x vec0` (c) `f(x)` is bounded (d) `f(x)=(log)_e x`