A cylindrical rod having temperature `T_(1)` and `T_(2)` at its ends. The rate of flow of heat is `Q_(1) cal//sec`. If all the linear dimensions are doubled keeping temperature constant, then rate of flow of heat `Q_(2)` will be
A. `4Q_1`
B. `2Q_2`
C. `Q_1/4`
D. `Q_1/2`