Right choice is (b) built up column lacings or battens are economical if load carrying members permit greater reduction in weight than what is added by lacing or batten
To explain I would say: Built up column lacings or battens are economical if load carrying members permit greater reduction in weight than what is added by lacing or batten. Built up column designed as axially loaded column may be accidentally loaded eccentrically or may have initial crookedness. Variable bending moment will be induced in such column because of eccentricity between centroidal axis of column and line of action of applied load due to this, there will be related shear stress force in plane of cross section and in connecting system.