A student performed the experiment to measure the speed of sound in air using resonance air-column method. Two resonances in the air-column were obtained by lowering the water level. The resonance with the shorter air-column is the first resonanceandthat with the longer air-column is the second resonance. Then,

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 prongsis typically around 1 cm

D

the length of the air-columnat the first resonance was somewhat shorter than $$\frac{1}{4}th$$ of the wavelength of the sound in air