The block diagram for the receiver is given as:A and B stand for

The correct answer is Option (4) → A-IF stage, B-Detector

In an amplitude modulation receiver the signal picked up by the antenna is weak, so it is first amplified. The carrier frequency is then lowered to an intermediate frequency in the IF stage to make further processing easier, the detector recovers the message from the modulated wave, and a final amplifier strengthens it.

So the order of the blocks is: antenna, amplifier, A = IF stage, B = Detector, amplifier, output.

The IF stage must come before the detector, so Option (1) has them in the wrong order; an oscillator, transistor, diode or LED is not a stage of this receiver chain (Options 2 and 3).

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Detection of Amplitude Modulated Wave – “The transmitted message gets attenuated in propagating through the channel. The receiving antenna is therefore to be followed by an amplifier and a detector. In addition, to facilitate further processing, the carrier frequency is usually changed to a lower frequency by what is called an intermediate frequency (IF) stage preceding the detection. The detected signal may not be strong enough to be made use of and hence is required to be amplified. A block diagram of a typical receiver is shown in Fig. 15.12”