Testing factorization in B -> D(*)X decays

In QCD the amplitude for B0 -> D()+pi- factorizes in the large Nc limit or in the large energy limit Q >> Lambda_QCD where Q = {m_b, m_c, m_b-m_c}. Data also suggests factorization in exclusive processes B-> D pi+ pi- pi- pi0 and B-> D* omega pi-, however by themselves neither large Nc nor large Q can account for this. Noting that the condition for large energy release in B0-> D+ pi- is enforced by the SV limit, m_b, m_c >> m_b-m_c >> Lambda, we propose that the combined large Nc and SV limits justify factorization in B -> D() X. This combined limit is tested with the inclusive decay spectrum measured by CLEO. We also give exact large Nc relations among isospin amplitudes for B -> D()X and B -> D() D-bar()X, which can be used to test factorization through exclusive or inclusive measurements. Predictions for the modes B-> D() pi pi, B-> D()K K-bar and B-> D() D-bar() K are discussed using available data.