4 rods of same material but with different radii & lengths are used to connect 2 reservoirs of heat with the same temperature difference. Which one will conduct more heat

@ sreenidhi 
the rods whose a/l ratio is more will conduct more amount of heat . 
as per the relation 
dq/dt = k (t1-t2) *a / l 
so, by solving that 
dq/dt is directly prop to a/l 
and if dq/dt will increase then a/l will also increase . 
HOPE IT CLEARS YOUR DOUBT 
ALL THE BEST ..