Bulky bases like potassium tert-butoxide (\((CH_3)_3CO^-K^+\)) strongly favour elimination (E2) over substitution. The steric bulk of the base prevents it from attacking the carbon centre (backside attack needed for SN2); instead, it abstracts a proton from the \(\beta\)-carbon to give elimination. SN1 requires no base. Therefore, with bulky bases and secondary/tertiary substrates, E2 is the predominant pathway.