A battery with an electromotive force (e.m.f.) of $6.0\,\text{V}$ and negligible internal resistance is joined to a voltmeter and four other components, as shown. The voltmeter is placed across points X and Y. Its positive terminal is linked to X, while its negative terminal is linked to Y. At the start, the resistance of each of the four components is $1.0\,\text{k}\Omega$. Which single change will make the voltmeter give a positive reading?
- ADecrease the temperature of the thermistor.
- BIncrease the resistance of the variable resistor.
- CReduce the intensity of light incident on the light-dependent resistor (LDR).
- DReplace the fixed resistor with a $500\,\Omega$ resistor.