In a gusseted base, when the end of the column is machined smooth for complete bearing, the axial load is transferred to base slab :

ANS:B - Fully by direct bearing

When the end of the column is machined for full bearing on the base plate, it is assumed that 50 % of the total design axial column load is transferred to the base plate by direct bearing and the remaining 50% of axial load will be transferred through fastenings like bolted or welded connection including gusset plate, stiffeners if any.

However, when the end of the column and gusset plate is not machined for full bearing i.e. partially machined, in that case, it is assumed that connection to the base plate is designed for all the forces acting on the plate.