Select the correct statements among the following :
A. Slow neutrons can cause fission in ${ }_{92}^{235} \mathrm{U} than fast neutrons.
B. \alpha-rays are Helium nuclei.
C. \beta-rays are fast moving electrons or positrons.
D. \gamma-rays are electromagnetic radiations of wavelengths larger than \mathrm{X}$-rays.
Choose the most appropriate answer from the options given below :