Solutions of two electrolytes $A$ and $B$ are diluted. The $\Lambda_m$ of $B$ increases $1.5$ times while that of $A$ increases $25$ times. Which of the two is a strong electrolyte? Justify your answer.

(B) Electrolyte $B$ is a strong electrolyte because,upon dilution,the number of ions remains constant,and only the interionic attraction decreases,leading to a small increase in $\Lambda_m$.
Electrolyte $A$ is a weak electrolyte because it does not undergo complete ionization. Upon dilution,the degree of dissociation increases significantly,leading to a large increase in the number of ions,which causes a drastic increase ($25$ times) in its $\Lambda_m$ value.
Therefore,$B$ is the strong electrolyte.