Thermistor's negative temperature coefficient increases current as temperature rises

Steps:

• The circuit has a battery, NTC thermistor, fixed resistor, and ammeter in series.
• As water temperature T increases, thermistor resistance R_t decreases (NTC property).
• Total resistance R_total = R_fixed + R_t decreases.
• Current I = V / R_total increases with T, so graph shows I rising.

Why B is correct:

• B depicts I increasing with T, matching I = V / (R_fixed + R_t) where R_t falls as T rises (NTC definition).

Why the others are wrong:

• A: Shows I decreasing, which would occur for PTC thermistor, not standard NTC.
• C: Shows constant I, implying unchanging resistance, but R_t varies with T.
• D: Shows I decreasing then increasing or irregular, not matching steady NTC behavior.

Final answer: B