Which of the glycosidic linkage between galactose and glucose is present in lactose?

According to molecular orbital theory, the species among the following that does not exist is :

Complete combustion of 1.80 g of an oxygen containing compound (C_xH_yO_z) gave 2.64 g of CO₂ and 1.08 g of H₂O. The percentage of oxygen in the organic compound is :

The hybridization and magnetic nature of $${[Mn{(CN)_6}]^{4 - }}$$ and $${[Fe{(CN)_6}]^{3 - }}$$, respectively are :