In [Mn(H2O)6]2+, the Mn2+ ion has the electronic configuration [Ar]3d5. Due to this configuration, the d-d transitions are symmetry forbidden because the 3d5 configuration is stable and does not easily undergo transitions.
In [Ti(H2O)6]3+, the Ti3+ ion has the electronic configuration [Ar]3d1. The single electron in the 3d1 configuration can undergo d-d transitions, making them symmetry allowed.
Thus, the d-d transitions in [Mn(H2O)6]2+ are symmetry forbidden, while those in [Ti(H2O)6]3+ are symmetry allowed.
The correct answer is (B)