The correct answer is: A. the signal is band-limited.
A band-limited signal is a signal whose frequency components are limited to a certain range. This means that the signal does not contain any frequencies that are higher than a certain frequency, called the bandwidth.
Perfect resolution is possible when the signal is band-limited because the signal can be perfectly reconstructed from its samples if the sampling rate is greater than twice the bandwidth. This is known as the Nyquist sampling theorem.
The other options are incorrect because they do not guarantee perfect resolution.
Option B: The signal is continuous. A continuous signal is a signal that can be represented by a function that is defined for all real numbers. However, a continuous signal cannot be perfectly represented by a finite number of samples. This is because there is always some error introduced when a continuous signal is sampled.
Option C: The signal is noiseless. A noiseless signal is a signal that does not contain any noise. However, all real-world signals contain some noise. This noise can introduce errors into the signal, which can reduce the resolution of the signal.
Option D: The signal is perfect. A perfect signal is a signal that has no errors. However, no real-world signal is perfect. All real-world signals contain some errors, which can reduce the resolution of the signal.