The reason that the TLC chamber should be kept closed with a lid on it is Select one:
a. to prevent temperature exchange
b. to prevent decomposition of compounds in the mixture
c. to maintain the gradient of the vapors in the chamber
d. to prevent evaporation of the sovent from the chamber

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.

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.