Let f be a function defined on the set of positive rational numbers with the property that f(a \cdot b)= f(a)+f(b) for all positive rational numbers a and b. Suppose that f also has the property that f(p)=p for every prime number p. For which of the following numbers x is f(x)<0 ?

**Answer Choices**

A. \dfrac{17}{32}

B. \dfrac{11}{16}

C. \dfrac{7}{9}

D. \dfrac{7}{6}

E. \dfrac{25}{11}