The correct answer is $\boxed{\text{B) 10.17 V}}$.
The zener diode has a breakdown voltage of 10 V. This means that when the voltage across the zener diode reaches 10 V, the zener diode will start to conduct current. The zener resistance is 8.5 W. This means that when a current of 20 mA flows through the zener diode, there will be a voltage drop of 0.17 V across the zener resistance. The additional voltage is the difference between the breakdown voltage and the voltage drop across the zener resistance. In this case, the additional voltage is 10 V – 0.17 V
= 10.17 V.Option A is incorrect because it is the voltage drop across the zener resistance. Option C is incorrect because it is the breakdown voltage of the zener diode. Option D is incorrect because it is the voltage drop across the zener diode plus the voltage drop across the zener resistance. Option E is incorrect because it is not one of the possible answers.