The books answer is D. No clue why though
Thank you for you effort
Welcome to PF captinkareem1!
It's a voltage divider, with resistances R1 and R2. The only difference from usual is that R1 is a temperature variable resistor, rather than a constant one. Can you write down an expression for the output voltage in terms of the input voltage, and the two resistances? Hint: it's a series circuit, so the same current has to flow everywhere, including through R1 and through R2. The expression you come up with should just be the standard voltage divider equation.
This will allow you to infer how R1 changes with T (does it increase or decrease) and therefore what you should do with it to get the desired dependence of V_out on T.
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