The compound lecithin is classified as a phospholipid. Phospholipids are a major component of cell membranes and are essential for various cellular functions. They consist of a glycerol backbone, two fatty acid tails (which are hydrophobic), and a phosphate group head (which is hydrophilic). This unique structure allows them to form bilayers, which are critical in cell membrane formation.
In contrast, the other options such as amino acids, glycerides, and carbohydrates refer to different types of biological molecules:
Therefore, the correct classification for lecithin is Phospholipids.
Three identical heat conducting rods are connected in series as shown in the figure. The rods on the sides have thermal conductivity 2K while that in the middle has thermal conductivity K. The left end of the combination is maintained at temperature 3T and the right end at T. The rods are thermally insulated from outside. In steady state, temperature at the left junction is \(T_1\) and that at the right junction is \(T_2\). The ratio \(T_1 / T_2\) is 
