The following demodulator scheme requires least $E_b/N_0$
- A. BPSK
- B. FSK
- C. ASK
- D. QAM
Answer: A. BPSK
Explanation: Among the given digital modulation schemes, BPSK (Binary Phase Shift Keying) has the lowest probability of error for a given $E_b/N_0$, meaning it requires the least signal energy per bit for reliable reception.