2.12 describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature

LDRs and Thermistors are components that can change their resistance (aka, it is not always the same).

An LDR (Light Dependant Resistor) changes its resistant depending on how much light falls on it. For example, in bright light the resistance is low and in darkness the resistance is at its highest.

A thermistor is a temperature-dependant resistor (its resistance changes depending on the temperature). For example, in hot conditions the resistance is low and in cooler conditions the resistance is high.