A radioactive source gives out three kinds of radiation, R, S and T. The diagram shows an experimental arrangement designed to investigate the penetrating ability of R, S and T. What are the identities of radiations R, S and T?
- A$\alpha$-particles, $\beta$-particles, $\gamma$-rays
- B$\alpha$-particles, $\gamma$-rays, $\beta$-particles
- C$\beta$-particles, $\alpha$-particles, $\gamma$-rays
- D$\gamma$-rays, $\beta$-particles, $\alpha$-particles