1011
10001
10101
101 E. None of the above
Answer is Wrong!
Answer is Right!
The correct answer is $\boxed{\text{D. }101}$.
A NOT gate is a logic gate that inverts its input signal. This means that if the input signal is 1, the output signal will be 0, and vice versa.
In this case, the input signal is $A=10100$. This can be represented as a binary number, which is $16$ in decimal. The output signal of the NOT gate is therefore $101$, which is $13$ in decimal.
Option A is incorrect because it is the complement of the output signal. Option B is incorrect because it is the complement of the input signal. Option C is incorrect because it is the complement of the output signal plus 1. Option E is incorrect because it is not a valid binary number.