Hyperconjugation is most useful for stabilising which of the...

On the basis of hyperconjugation, stability order of different alkyl carbocations is $3^{\circ}\gt2^{\circ}\gt1^{\circ}\gt$ methyl In $t$-butyl cation, the C -atom bearing the positive charge is attached to three methyl groups, thus it will have maximum hyperconjugate structures, which give it maximum stability.