  We propose a monodromy invariant pairing $K_{hol}(X) \otimes H_3(X^\vee,\ZZ)
\to \IQ$ for a mirror pair of Calabi-Yau manifolds, $(X,X^\vee)$. This pairing
is utilized implicitly in the previous calculations of the prepotentials for
Gromov-Witten invariants. After identifying the pairing explicitly we interpret
some hypergeometric series from the viewpoint of homological mirror symmetry
due to Kontsevich. Also we consider the local mirror symmetry limit to del
Pezzo surfaces in Calabi-Yau 3-folds.
