Three rods of identical cross-section and lengths are made of three different materials of thermal conductivity \(K _{1}, K _{2},\) and \(K _{3}\), respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at \(100^{\circ} C\) and the ther at \(0^{\circ} C\) (see figure). If the joints of the rod are at  \(70^{\circ} C\) and \(20^{\circ} C\) in steady state and there is no loss of energy from the surface of the rod, the correct relationship between \(K _{1}, K _{2}\) and \(K _{3}\) is 

1. A \(K _{1}: K _{3}=2: 3 ; K _{2}: K _{3}=2: 5\)
2. B \(K _{1}< K _{2}< K _{3}\)
3. C \(K _{1}: K _{2}=5: 2 ; K _{1}: K _{3}=3: 5\)
4. D \(K _{1}> K _{2}> K _{3}\)