| As shown in figures "A", "B", "C", "D" and "E" of the illustration pertaining to various diagrams specific to a PLC controlled temperature control system using a thermistor and operational amplifier, which statement is true? |
| A) The thermistor is a normally closed switch which opens on a temperature rise and closes on a temperature fall. |
| B) The thermistor is a normally open switch which closes on a temperature rise and opens on a temperature fall. |
| C) The thermistor is a resistance that varies inversely with temperature. |
| D) The thermistor is a resistance that varies directly with temperature. |
