Solution

The correct answer is Sampling rate must be at least 2 times the highest frequency contained in the signal.

Key Points

• The Nyquist theorem, also known as the Nyquist-Shannon sampling theorem, states that in order to accurately reconstruct an analog signal from its samples, the sampling rate must be at least twice the highest frequency present in the original signal.
• This minimum sampling rate is known as the Nyquist rate. If the sampling rate is lower than this, aliasing can occur, which means different signal frequencies become indistinguishable and the original signal cannot be properly reconstructed.

Therefore, the correct condition is: Sampling rate must be at least 2 times the highest frequency contained in the signal.