Answer:
d. to prevent evaporation of the solvent from the chamber.
Explanation:
TLC or thin layer chromatography is a technique which is used to separate the compounds on the basis of a principal that the different compounds have different solubility and adsorption to the two phases solid and liquid. It is also known as solid liqiud technique in which solid serves as a stationary base and liquid as a mobile phase. Solvent in the chamber should be ina small amount such that a little of bottom part of the plate below the spot should dipped in it. The lid of the chamber should be kept closed to avoid evapouration of solvent.