Step 1: Formula for harmonic mean.
The harmonic mean is given by \( H = \frac{2PQ}{P + Q} \). Using this formula, we can simplify the expression \( \frac{H}{P} + \frac{H}{Q} \).
Step 2: Conclusion.
Thus, the correct answer is option (B).
Final Answer:
\[
\boxed{\text{(B) } \frac{P + Q}{PQ}}
\]