A cyclindrical rod having temperature $T_1$ and $T_2$ at its end. The rate of flow of heat $Q_1$ cal/sec. If all the linear dimension are doubled keeping temperature remain const. then rate of flow of heat $Q_2$ will be :-

Question

( A ) 4 $Q_1$
( B ) $\frac{Q_1}{4}$
( C ) $2 Q_1$
( D ) $\frac{Q_1}{2}$