15 V
16 V
7.5 V
Answer is Right!
Answer is Wrong!
The correct answer is $\boxed{\text{A}}$.
When two voltage sources are connected in series-aiding form, the total voltage is the sum of the individual voltages. In this case, the total voltage is $6 V + 9 V = 15 V$.
Option B is incorrect because it is the sum of the two voltages plus 1 volt. Option C is incorrect because it is the average of the two voltages. Option D is incorrect because it is the difference of the two voltages. Option E is incorrect because it is not a valid option.