A platform seating the source of sound emitting sound of frequency n and two detectors `D_(1)` and `D_2` (S, `D_(1)` & `D_2` are at rest with respect to.ihe platform) is moving with a constant velocity of `5ms^(-1)` with respect to ground towards a vcrticarwall which in turn is moving away from the platform with a speed of `5 ms^(-1)` with respect to ground. Stationary detectors `D_3` and `D_4` are positioned behind the platform and between the platform and the wall as shown in the figure. Speed of sound in still air is `V= 340 ms^(-1)` . Take `lambda = V//n`. In matching the two columns consider the sound received by the detectors directly from the source and also after reflection from the wall. Air is still with respect to ground.

Answer

A-pq; B-pqs; C-q; D-qrs