A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor is/are

If E be electric field, then current density j = $\mathrm{\sigma }$E
Also we know that current density j = i/A
Hence j is different for different area of cross-sections. When j is different, then E is also different. Thus E is not constant. The drift velocity v_d is given be ${\mathrm{v}}_{\mathrm{d}}=\frac{\mathrm{j}}{\mathrm{ne}}=$ different J values. Hence only current i will be constant.