B0-->D(*-)a(+)(1): chirality tests and resolving an ambiguity in the CP violation parameter 2beta+gamma

We point out that the decays of B mesons into a vector meson and an axial-vector meson can distinguish between left and right-handed polarized mesons, in contrast to decays into two vector mesons. Measurements in B0-->D(*-)a(+)(1) are proposed for testing factorization and the V-A structure of the b-->c current, and for resolving a discrete ambiguity in 2beta+gamma.