An adiabatic process is defined as one in which no heat is exchanged between the system and its surroundings, so (q = 0) by definition. Applying the first law: (\Delta \cup = q - w = 0 - w = -w). During compression, work is done ON the gas by the surroundings, so (w < 0) (work done by the system is negative in compression). Therefore (\Delta \cup = -w > 0), meaning internal energy increases. For an ideal gas, internal energy depends only on temperature, so an increase in (U) implies an increase in (T). This is why a bicycle pump gets warm during rapid inflation — an example of adiabatic compression. Option B describes adiabatic expansion, not compression. Option C is wrong because heat exchange (q > 0) contradicts the adiabatic condition. Option D would apply to an isothermal process for an ideal gas, not an adiabatic one. This is a concept-rich NCERT topic distinguishing adiabatic from isothermal processes. Plausibility check: compressing any gas does work on it, increasing its energy and temperature, regardless of the working substance.