The correct answer is: A. Gives rise to aperture effect.
Flat top sampling of low pass signals gives rise to aperture effect. This is because the sampling process is not ideal and there is a finite width to the sampling pulse. This results in a loss of information at the higher frequencies, which can be seen as a “smearing” of the signal.
The other options are incorrect. Oversampling is the process of sampling a signal at a higher rate than the Nyquist rate. This can be done to improve the accuracy of the sampling process or to reduce aliasing. Aliasing is the phenomenon that occurs when a signal is sampled at a rate below the Nyquist rate. This results in the creation of spurious signals, which can be seen as “ghosts” of the original signal. Delay distortion is a type of distortion that occurs when a signal is sampled and then reconstructed. This distortion is caused by the delay that occurs between the sampling and reconstruction processes.