A circuit has two different voltage sources that are connected in a series-opposing form. If the sources are rated at 6 V and 9 V, what is the total source voltage? A. 3 V B. 16 V C. 7.5 V D. 8 V E. None of the above

3 V
16 V
7.5 V
8 V E. None of the above

The correct answer is $\boxed{\text{D}}$.

When two voltage sources are connected in series-opposing form, the total voltage is the difference between the two source voltages. In this case, the total voltage is $9 \text{ V} – 6 \text{ V} =

3 \text{ V}$.

Option A is incorrect because it is the sum of the two source voltages. Option B is incorrect because it is twice the sum of the two source voltages. Option C is incorrect because it is the average of the two source voltages. Option E is incorrect because it is not a possible value for the total source voltage.