$(A)$ the intensity of the sound heard at the first resonance was more than that at the second resonance
$(B)$ the prongs of the tuning fork were kept in a horizontal plane above the resonance tube
$(C)$ the amplitude of vibration of the ends of the prongs is typically around $1 \mathrm{~cm}$
$(D)$ the length of the air-column at the first resonance was somewhat shorter than $1 / 4$ th of the wavelength of the sound in air
Statement $-2$ : Due to the motion of source, wavelength of the sound waves (emitted by source) as received by stationary listener is affected.
Statement $-3$ : If receiver and source both are moving, the observed frequency must be different from the original frequency of source.
Treat motion of source or listener as always along a line joining them for all above cases.