Two identical vessels are filled with equal amounts of ice. The vessels are made from different materials. If the ice melts in the two vessels in times `t_(1) and t_(2)` respectively, then their thermal conductivities are in the ratio
A. `t_(1)/t_(2)`
B. `t_(2)/t_(1)`
C. `t_(2)^(2):t_(1)^(2)`
D. `t_(1)^(2):t_(2)^(2)`