Electrons in a cathode ray tube have been emitted with a velocity...

(A) ${V}_{e} = 1000m / s; h = 6 \times {10}^{- 34}Js$

${m}_{e} = 9 \times {10}^{- 31}kg$
Debroglie wavelength:

$⇒ \lambda = \dfrac{h}{mv} = \dfrac{6 \times {10}^{- 34}}{9 \times {10}^{- 31} \times 1000} = 666 . 67 \times {10}^{- 9}m$

$= 666 . 67nm$

(B) The characteristic of electrons emitted is independent of the material of the electrodes of the cathode ray tube. Electrons are fundamental to all traditional forms of matter.

(C) The cathode rays start from cathode and move towards anode. It was discovered by Sir J.J. Thompson.

(D) The nature of the emitted electrons is independent on the nature of the gas present in cathode ray tube. They are fundamental particles.