Within the limitations of small perturbation theory, at a given transonic Mach number, aircraft with the same longitudinal distribution of cross-sectional area, including fuselage, wings and all appendages will, at zero lift, have the same wave drag.

Why: Mach waves under transonic conditions are perpendicular to flow.

Implication:

Keep area distribution smooth, constant if possible. Else, strong shocks and hence drag result.
 

Wing-body interaction leading to shock formation:

Observed: c_p distributions are such that maximum velocity is reached far aft at root and far forward at tip.
Hence, streamlines curves in at the root, compress, shock propagates out.